[424B2] Citigroup Inc. Prospectus Supplement

Rhea-AI Filing Summary

Morgan Stanley Finance LLC is offering $1.097 million aggregate principal amount of five-year Market-Linked Notes (Series A) that mature on 5 July 2030 and are fully and unconditionally guaranteed by Morgan Stanley. The notes are linked to the S&P 500 Futures Excess Return Index (ticker SPXFP) and are designed to provide principal protection at maturity with leveraged upside exposure.

• Issue & pricing: Denomination $1,000; issue price $1,000; estimated value on the 30 June 2025 pricing date $966.60, reflecting embedded distribution and hedging costs.
• Return profile: • If the final index level > initial level (514.49), investors receive $1,000 plus 133 % of the index appreciation. • If the final level ≤ initial level, only the principal is repaid. No interim coupons are paid.
• Key dates: Strike/Pricing 30 Jun 2025; Original issue 3 Jul 2025; Observation 1 Jul 2030; Maturity 5 Jul 2030.
• Distribution economics: Sold exclusively to fee-based advisory accounts. Agent (MS & Co.) commissions/fees equal $7.50 (0.75 %) per note; selected dealers may earn up to $6.25 structuring fee. Net proceeds to issuer $992.50 per note.
• Liquidity & listing: The notes will not be listed; MS & Co. may provide a secondary market but is not obligated to do so. Secondary prices likely to be below par and below the estimated value once bid-offer and credit spreads are considered.
• Credit considerations: Payment depends solely on the credit of Morgan Stanley (A-/A1) and its finance subsidiary; the product is unsecured and unsubordinated.
• Risk highlights: • No periodic income and potential zero upside if the index is flat or down.
  • Market value highly sensitive to index volatility, interest-rate moves and MS credit spreads.
  • Tax treatment as a contingent payment debt instrument; U.S. holders must accrue OID at a comparable yield of 4.5259 %.

In essence, the notes suit investors seeking principal protection plus enhanced equity participation within a discretionary advisory framework, willing to accept liquidity, credit and tax complexities and to forego dividend income and total-return benefits of direct equity or ETF exposure.

Positive

• 133 % participation rate on upside provides leveraged exposure relative to traditional principal-protected notes, potentially enhancing returns if the S&P 500 futures index rallies.
• Full repayment of principal at maturity offers downside protection absent issuer default, appealing to risk-averse clients.
• Morgan Stanley guarantee adds credit strength versus non-rated issuers, supporting repayment confidence.

Negative

• No interim coupons or dividend capture means five years of zero income and underperformance versus total-return benchmarks.
• Estimated value is $966.60, a 3.3 % discount to issue price, indicating immediate mark-to-market drag for buy-and-hold investors.
• Illiquid secondary market; notes are unlisted and rely on a single dealer, leading to potentially wide bid-ask spreads.
• Credit risk of Morgan Stanley remains despite principal protection, exposing holders to downgrade or default scenarios.
• Complex tax treatment as contingent payment debt instrument requires OID accrual and may convert gains into ordinary income.

Insights

Structured Products Analyst

TL;DR 5-year principal-protected notes offer 133 % upside but no coupons; estimated value 3.3 % below par, liquidity limited, credit risk applies.

The structure delivers leveraged participation to SPXFP while guaranteeing return of principal at maturity. A 133 % participation is attractive versus typical 120-125 % levels seen in recent deals, especially given MS's A-level credit. However, the embedded cost gap (par vs. $966.60 estimated value) translates into a 3.3 % upfront inefficiency investors must recoup through index performance. With no interim coupons, breakeven on a hold-to-maturity basis requires roughly 2.5 % index appreciation; higher when considering opportunity cost of foregone income. Because the index reflects excess return on E-mini futures, investors miss S&P 500 dividends, meaning required total market appreciation is even higher than headline percentages suggest. Secondary-market depth is uncertain: lack of listing and single-dealer market making imply potentially wide spreads. Overall impact is neutral: suitable for niche advisory portfolios but not a broad game-changer for MS or the market.

Portfolio Manager – Multi-Asset

TL;DR Notes give cheap downside hedge (principal back) yet upside capped to 133 % of futures ER; poor liquidity and tax drag dampen appeal.

From an allocation standpoint, the product competes with buffered ETFs and structured CDs. Principal protection reduces tail risk, but opportunity cost is considerable: investors receive neither dividends nor alternative income streams for five years. The excess-return index underperforms the total-return S&P 500 by the dividend yield (~1.5-2 % annually), effectively shaving roughly 8-10 % cumulative performance versus TR exposure over the term. Credit exposure to MS must be sized within overall counterparty limits; although MS is investment-grade, widening spreads could pressure secondary valuations. Implementation risk is elevated for tactical users given uncertain exit pricing. For strategic buy-and-hold investors comfortable with the tax treatment and credit profile, the notes can act as a partial equity replacement in conservative sleeves, but do not materially change the portfolio opportunity set.

Citigroup Global Markets Holdings Inc. June 30, 2025 Medium-Term Senior Notes, Series N Pricing Supplement No. 2025-USNCH27097 Filed Pursuant to Rule 424(b)(2) Registration Statement Nos. 333-270327 and 333-270327-01

Dual Directional Buffer Securities with Autocallable Feature Linked to the Worst Performing of the Nasdaq-100 Index^® and the S&P 500^® Index Due July 6, 2027

▪ The securities offered by this pricing supplement are unsecured debt securities issued by Citigroup Global Markets Holdings Inc. and guaranteed by Citigroup Inc.  Unlike conventional debt securities, the securities do not pay interest, do not repay a fixed amount of principal at maturity and are subject to potential automatic early redemption. Your return on the securities will depend on the performance of the worst performing of the underlyings specified below.

▪ The securities offer the opportunity for automatic early redemption at a premium if the closing value of the worst performing underlying on the interim valuation date is greater than or equal to its initial underlying value.  If the closing value of the worst performing underlying on the interim valuation date is less than the initial underlying value, the securities will not be automatically redeemed at a premium and, instead, the securities offer modified exposure to the performance of the worst performing underlying, with (i) the opportunity to participate in any potential appreciation of the worst performing underlying at the upside participation rate specified below, (ii) the opportunity for a positive return at maturity if the worst performing underlying depreciates within a limited range (not more than the buffer percentage specified below) based on the absolute value of that depreciation and (iii) a limited buffer against any depreciation of the worst performing underlying in excess of the buffer percentage. In exchange for these features, investors in the securities must be willing to forgo (i) any dividends with respect to the underlyings and (ii) any positive participation in the absolute value of any depreciation of the worst performing underlying if the worst performing underlying depreciates by more than the buffer percentage. In addition, investors in the securities must be willing to accept downside exposure to any depreciation of the worst performing underlying on the final valuation date in excess of the buffer percentage. If the securities are not automatically redeemed and the worst performing underlying depreciates by more than the buffer percentage from its initial underlying value to its final underlying value, you will lose 1% of the stated principal amount of your securities for every 1% by which that depreciation exceeds the buffer percentage.

▪ You will be subject to risks associated with each of the underlyings and will be negatively affected by adverse movements in any one of the underlyings.

▪ In order to obtain the modified exposure to the worst performing underlying that the securities provide, investors must be willing to accept (i) an investment that may have limited or no liquidity and (ii) the risk of not receiving any amount due under the securities if we and Citigroup Inc. default on our obligations. All payments on the securities are subject to the credit risk of Citigroup Global Markets Holdings Inc. and Citigroup Inc.

KEY TERMS
Issuer:	Citigroup Global Markets Holdings Inc., a wholly owned subsidiary of Citigroup Inc.
Guarantee:	All payments due on the securities are fully and unconditionally guaranteed by Citigroup Inc.

Underlyings:	Underlying	Initial underlying value*	Final buffer value**
	Nasdaq-100 Index®	22,679.01	19,277.159
	S&P 500® Index	6,204.95	5,274.208
	*For each underlying, its closing value on the pricing date **For each underlying, 85.00% of its initial underlying value

Stated principal amount:	$1,000 per security
Pricing date:	June 30, 2025
Issue date:	July 3, 2025
Interim valuation date:	June 30, 2026, subject to postponement if such date is not a scheduled trading day or certain market disruption events occur
Final valuation date:	June 30, 2027, subject to postponement if such date is not a scheduled trading day or certain market disruption events occur
Automatic early redemption:	If the closing value of the worst performing underlying on the interim valuation date is greater than or equal to its initial underlying value, the securities will be automatically redeemed on the third business day immediately following the interim valuation date for an amount in cash per security equal to $1,000 plus the premium applicable to the interim valuation date.  If the securities are automatically redeemed following the interim valuation date, they will cease to be outstanding.
Maturity date:	July 6, 2027
Payment at maturity:	If the securities have not been previously redeemed, you will receive at maturity for each security you then hold: ▪  If the final underlying value of the worst performing underlying on the final valuation date is greater than or equal to its initial underlying value: $1,000 + the upside return amount ▪  If the final underlying value of the worst performing underlying on the final valuation date is less than its initial underlying value but greater than or equal to its final buffer value: $1,000 + the absolute return amount ▪  If the final underlying value of the worst performing underlying on the final valuation date is less than its final buffer value: $1,000 + [$1,000 × (the underlying return of the worst performing underlying on the final valuation date + the buffer percentage)] If the securities are not automatically redeemed and the final underlying value of the worst performing underlying on the final valuation date is less than its final buffer value, you will receive less, and possibly significantly less, than the stated principal amount of your securities at maturity.
Upside return amount:	$1,000 × the underlying return of the worst performing underlying on the final valuation date × the upside participation rate
Upside participation rate:	150%
Absolute return amount:	$1,000 × the absolute value of the underlying return of the worst performing underlying on the final valuation date
Buffer percentage:	15%
Listing:	The securities will not be listed on any securities exchange
Underwriter:	Citigroup Global Markets Inc. (“CGMI”), an affiliate of the issuer, acting as principal
Underwriting fee and issue price:	Issue price(1)	Underwriting fee(2)	Proceeds to issuer(3)
Per security:	$1,000.00	$10.00	$990.00
Total:	$1,996,000.00	$12,175.60	$1,983,824.40

(1) On the date of this pricing supplement, the estimated value of the securities is $986.00 per security, which is less than the issue price. The estimated value of the securities is based on CGMI’s proprietary pricing models and our internal funding rate. It is not an indication of actual profit to CGMI or other of our affiliates, nor is it an indication of the price, if any, at which CGMI or any other person may be willing to buy the securities from you at any time after issuance. See “Valuation of the Securities” in this pricing supplement.

(2) CGMI will receive an underwriting fee of up to $10.00 for each security sold in this offering.  The total underwriting fee and proceeds to issuer in the table above give effect to the actual total underwriting fee.  For more information on the distribution of the securities, see “Supplemental Plan of Distribution” in this pricing supplement. In addition to the underwriting fee, CGMI and its affiliates may profit from hedging activity related to this offering, even if the value of the securities declines. See “Use of Proceeds and Hedging” in the accompanying prospectus.

(3) The per security proceeds to issuer indicated above represent the minimum per security proceeds to issuer for any security, assuming the maximum per security underwriting fee. As noted above, the underwriting fee is variable.

Investing in the securities involves risks not associated with an investment in conventional debt securities. See “Summary Risk Factors” beginning on page PS-7.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities or determined that this pricing supplement and the accompanying product supplement, underlying supplement, prospectus supplement and prospectus are truthful or complete. Any representation to the contrary is a criminal offense.

You should read this pricing supplement together with the accompanying product supplement, underlying supplement, prospectus supplement and prospectus, which can be accessed via the hyperlinks below:

Product Supplement No. EA-02-10 dated March 7, 2023 Underlying Supplement No. 11 dated March 7, 2023 Prospectus Supplement and Prospectus each dated March 7, 2023 The securities are not bank deposits and are not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency, nor are they obligations of, or guaranteed by, a bank.

KEY TERMS (continued)
Premium:	The premium applicable to the interim valuation date is the percentage of the stated principal amount set forth below. The premium may be significantly less than the appreciation of any underlying from the pricing date to the interim valuation date. •     June 30, 2026:              10.00% of the stated principal amount
Final underlying value:	For each underlying, its closing value on the final valuation date
Worst performing underlying:	For any valuation date, the underlying with the lowest underlying return determined as of that valuation date
Underlying return:	For each underlying on any valuation date, (i) its closing value on that valuation date minus its initial underlying value, divided by (ii) its initial underlying value
CUSIP / ISIN:	17331JCA8 / US17331JCA88

Citigroup Global Markets Holdings Inc.

Additional Information

The terms of the securities are set forth in the accompanying product supplement, prospectus supplement and prospectus, as supplemented by this pricing supplement.  The accompanying product supplement, prospectus supplement and prospectus contain important disclosures that are not repeated in this pricing supplement.  For example, the accompanying product supplement contains important information about how the closing value of each underlying will be determined and about adjustments that may be made to the terms of the securities upon the occurrence of market disruption events and other specified events with respect to each underlying.  The accompanying underlying supplement contains information about each underlying that is not repeated in this pricing supplement.  It is important that you read the accompanying product supplement, underlying supplement, prospectus supplement and prospectus together with this pricing supplement in connection with your investment in the securities.  Certain terms used but not defined in this pricing supplement are defined in the accompanying product supplement.

PS-3

Citigroup Global Markets Holdings Inc.

Payout Diagram

The diagram below illustrates your payment at maturity of the securities, assuming the securities have not previously been automatically redeemed, for a range of hypothetical underlying returns of the worst performing underlying on the final valuation date. Your payment at maturity (if the securities are not earlier automatically redeemed) will be determined based solely on the final underlying value of the worst performing underlying on the final valuation date.

Investors in the securities will not receive any dividends with respect to the underlyings. The diagram and examples below do not show any effect of lost dividend yield over the term of the securities. See “Summary Risk Factors—You will not receive dividends or have any other rights with respect to the underlyings” below.

Payout Diagram
n The Securities	n The Worst Performing Underlying

PS-4

Citigroup Global Markets Holdings Inc.

Hypothetical Examples of the Payment at Maturity

The table below indicates what your payment at maturity and total return on the securities would be for various hypothetical underlying returns of the worst performing underlying on the final valuation date.  Your actual payment at maturity and total return on the securities will depend on the actual final underlying value of the worst performing underlying on the final valuation date.

Hypothetical Underlying Return of the Worst Performing Underlying	Hypothetical Payment at Maturity per Security	Hypothetical Total Return on Securities at Maturity(1)
100.00%	$2,500.00	150.00%
90.00%	$2,350.00	135.00%
70.00%	$2,050.00	105.00%
50.00%	$1,750.00	75.00%
40.00%	$1,600.00	60.00%
30.00%	$1,450.00	45.00%
20.00%	$1,300.00	30.00%
10.00%	$1,150.00	15.00%
0.00%	$1,000.00	0.00%
-10.00%	$1,100.00	10.00%
-15.00%	$1,150.00	15.00%
-15.01%	$999.90	-0.01%
-20.00%	$950.00	-5.00%
-30.00%	$850.00	-15.00%
-40.00%	$750.00	-25.00%
-50.00%	$650.00	-35.00%
-100.00%	$150.00	-85.00%

⁽¹⁾ Hypothetical total return on securities at maturity = (i) hypothetical payment at maturity per security minus $1,000 stated principal amount per security, divided by (ii) $1,000 stated principal amount per security

The examples below are intended to illustrate how, if the securities are not automatically redeemed prior to maturity, your payment at maturity will depend on the final underlying value of the worst performing underlying on the final valuation date. Your actual payment at maturity per security, if the securities are not automatically redeemed prior to maturity, will depend on the actual final underlying value of the worst performing underlying on the final valuation date. The examples are solely for illustrative purposes, do not show all possible outcomes and are not a prediction of any payment that may be made on the securities.

The examples below are based on the following hypothetical values and do not reflect the actual initial underlying values or final buffer values of the underlyings.  For the actual initial underlying value and final buffer value of each underlying, see the cover page of this pricing supplement.  We have used these hypothetical values, rather than the actual values, to simplify the calculations and aid understanding of how the securities work.  However, you should understand that the actual payment at maturity on the securities will be calculated based on the actual initial underlying value and final buffer value of each underlying, and not the hypothetical values indicated below.

Underlying	Hypothetical initial underlying value	Hypothetical final buffer value
Nasdaq-100 Index®	100	85.00 (85.00% of its hypothetical initial underlying value)
S&P 500® Index	100	85.00 (85.00% of its hypothetical initial underlying value)

Example 1—Upside Scenario A. The final underlying value of the worst performing underlying on the final valuation date is 110, resulting in a 10% underlying return for the worst performing underlying.  In this example, the final underlying value of the worst performing underlying on the final valuation date is greater than its initial underlying value.

Underlying	Hypothetical final underlying value	Hypothetical underlying return
Nasdaq-100 Index®*	110	10%
S&P 500® Index	150	50%

*Worst performing underlying

Payment at maturity per security = $1,000 + the upside return amount

= $1,000 + ($1,000 × the underlying return of the worst performing underlying × the upside participation rate)

= $1,000 + ($1,000 × 10% × 150%)

= $1,000 + $150

= $1,150

PS-5

Citigroup Global Markets Holdings Inc.

In this scenario, the worst performing underlying has appreciated from its initial underlying value to its final underlying value, and your total return at maturity would equal the underlying return of the worst performing underlying multiplied by the upside participation rate.

Example 2—Upside Scenario B. The final underlying value of the worst performing underlying on the final valuation date is 90, resulting in a -10% underlying return for the worst performing underlying.  In this example, the final underlying value of the worst performing underlying on the final valuation date is less than its initial underlying value but greater than its final buffer value.

Underlying	Hypothetical final underlying value	Hypothetical underlying return
Nasdaq-100 Index®	115	15%
S&P 500® Index*	90	-10%

*Worst performing underlying

Payment at maturity per security = $1,000 + the absolute return amount
= $1,000 + ($1,000 × the absolute value of the underlying return of the worst performing underlying)

= $1,000 + ($1,000 × |-10%|)

= $1,000 + $100

= $1,100

In this scenario, the worst performing underlying has depreciated from its initial underlying value to its final underlying value, but not below its final buffer value. As a result, your total return at maturity in this scenario would reflect 1-to-1 positive exposure to the absolute value of the negative performance of the worst performing underlying.

Example 3—Downside Scenario. The final underlying value of the worst performing underlying on the final valuation date is 30, resulting in a -70% underlying return for the worst performing underlying.  In this example, the final underlying value of the worst performing underlying on the final valuation date is less than its final buffer value.

Underlying	Hypothetical final underlying value	Hypothetical underlying return
Nasdaq-100 Index®	120	20%
S&P 500® Index*	30	-70%

*Worst performing underlying

Payment at maturity per security = $1,000 + [$1,000 × (the underlying return of the worst performing underlying + the buffer percentage)]

= $1,000 + [$1,000 × (-70% + 15%)]

= $1,000 + [$1,000 × -55%]

= $1,000 + -$550

= $450

In this scenario, the worst performing underlying has depreciated from its initial underlying value to its final underlying value by more than the buffer percentage. As a result, your total return at maturity in this scenario would be negative and would reflect 1-to-1 exposure to the negative performance of the worst performing underlying beyond the buffer percentage.

PS-6

Citigroup Global Markets Holdings Inc.

Summary Risk Factors

An investment in the securities is significantly riskier than an investment in conventional debt securities. The securities are subject to all of the risks associated with an investment in our conventional debt securities (guaranteed by Citigroup Inc.), including the risk that we and Citigroup Inc. may default on our obligations under the securities, and are also subject to risks associated with each underlying.  Accordingly, the securities are suitable only for investors who are capable of understanding the complexities and risks of the securities. You should consult your own financial, tax and legal advisors as to the risks of an investment in the securities and the suitability of the securities in light of your particular circumstances.

The following is a summary of certain key risk factors for investors in the securities.  You should read this summary together with the more detailed description of risks relating to an investment in the securities contained in the section “Risk Factors Relating to the Securities” beginning on page EA-7 in the accompanying product supplement. You should also carefully read the risk factors included in the accompanying prospectus supplement and in the documents incorporated by reference in the accompanying prospectus, including Citigroup Inc.’s most recent Annual Report on Form 10-K and any subsequent Quarterly Reports on Form 10-Q, which describe risks relating to the business of Citigroup Inc. more generally.

▪ You may lose a significant portion of your investment. Unlike conventional debt securities, the securities do not repay a fixed amount of principal at maturity. Instead, if the securities are not automatically redeemed, your payment at maturity will depend on the performance of the worst performing underlying.  If the worst performing underlying depreciates by more than the buffer percentage from its initial underlying value to its final underlying value, the absolute return feature will no longer be available and you will lose 1% of the stated principal amount of your securities for every 1% by which that depreciation exceeds the buffer percentage.

▪ If the securities are automatically redeemed, the appreciation potential of the securities is limited by the premium specified for the interim valuation date. If the closing value of the worst performing underlying on the interim valuation date is greater than or equal to its initial underlying value, you will be repaid the stated principal amount of your securities and will receive the premium applicable to the interim valuation date, regardless of how significantly the closing value of the worst performing underlying the interim valuation date may exceed the initial underlying value. Accordingly, the premium may result in a return on the securities that is significantly less than the return you could have achieved on a direct investment the worst performing underlying.

▪ The securities may be automatically redeemed prior to maturity, limiting the term of the securities. If the closing value of the worst performing underlying on the interim valuation date is greater than or equal to its initial underlying value, the securities will be automatically redeemed.  If the securities are automatically redeemed following the interim valuation date, they will cease to be outstanding. Moreover, you may not be able to reinvest your funds in another investment that provides a similar yield with a similar level of risk.

▪ Your potential for positive return from depreciation of the worst performing underlying is limited. The return potential of the securities in the event that the final underlying value of the worst performing underlying on the final valuation date is less than its initial underlying value is limited to the buffer percentage. Any decline in the final underlying value of the worst performing underlying on the final valuation date below its final buffer value will result in a loss, rather than a positive return, on the securities.

▪ The securities do not pay interest. Unlike conventional debt securities, the securities do not pay interest or any other amounts prior to maturity. You should not invest in the securities if you seek current income during the term of the securities.

▪ The securities are subject to heightened risk because they have multiple underlyings.  The securities are more risky than similar investments that may be available with only one underlying. With multiple underlyings, there is a greater chance that any one underlying will perform poorly, adversely affecting your return on the securities.

▪ The securities are subject to the risks of each of the underlyings and will be negatively affected if any one underlying performs poorly.  You are subject to risks associated with each of the underlyings. If any one underlying performs poorly, you will be negatively affected, regardless of the performance of any other underlying. The securities are not linked to a basket composed of the underlyings, where the blended performance of the underlyings would be better than the performance of the worst performing underlying alone.  Instead, you are subject to the full risks of whichever of the underlyings is the worst performing underlying.

▪ You will not benefit in any way from the performance of any better performing underlying.  The return on the securities depends solely on the performance of the worst performing underlying, and you will not benefit in any way from the performance of any better performing underlying.

▪ You will be subject to risks relating to the relationship between the underlyings.  It is preferable from your perspective for the underlyings to be correlated with each other, in the sense that their closing values tend to increase or decrease at similar times and by similar magnitudes.  By investing in the securities, you assume the risk that the underlyings will not exhibit this relationship.  The less correlated the underlyings, the more likely it is that any one of the underlyings will perform poorly over the term of the securities. All that is necessary for the securities to perform poorly is for one of the underlyings to perform poorly.  It is impossible to predict what the relationship between the underlyings will be over the term of the securities.  The underlyings differ in significant ways and, therefore, may not be correlated with each other.

PS-7

Citigroup Global Markets Holdings Inc.

▪ You will not receive dividends or have any other rights with respect to the underlyings. You will not receive any dividends with respect to the underlyings. This lost dividend yield may be significant over the term of the securities. The payment scenarios described in this pricing supplement do not show any effect of lost dividend yield over the term of the securities. In addition, you will not have voting rights or any other rights with respect to the underlyings or the stocks included in the underlyings.

▪ The performance of the securities will depend on the closing values of the underlyings solely on the final and interim valuation dates, which makes the securities particularly sensitive to volatility in the closing values of the underlyings on or near the valuation dates.  Whether the securities will be automatically redeemed prior to maturity will depend on the closing values of the underlyings solely on the interim valuation date, regardless of the closing values of the underlyings on other days during the term of the securities. If the securities are not automatically redeemed prior to maturity, what you receive at maturity will depend solely on the final underlying value of the worst performing underlying on the final valuation date, and not on any other day during the term of the securities. Because the performance of the securities depends on the closing values of the underlyings on a limited number of dates, the securities will be particularly sensitive to volatility in the closing values of the underlyings on or near the valuation dates. You should understand that the closing value of each underlying has historically been highly volatile.

▪ The securities are subject to the credit risk of Citigroup Global Markets Holdings Inc. and Citigroup Inc.  If we default on our obligations under the securities and Citigroup Inc. defaults on its guarantee obligations, you may not receive anything owed to you under the securities.

▪ The securities will not be listed on any securities exchange and you may not be able to sell them prior to maturity.  The securities will not be listed on any securities exchange. Therefore, there may be little or no secondary market for the securities.  CGMI currently intends to make a secondary market in relation to the securities and to provide an indicative bid price for the securities on a daily basis.  Any indicative bid price for the securities provided by CGMI will be determined in CGMI’s sole discretion, taking into account prevailing market conditions and other relevant factors, and will not be a representation by CGMI that the securities can be sold at that price, or at all.  CGMI may suspend or terminate making a market and providing indicative bid prices without notice, at any time and for any reason.  If CGMI suspends or terminates making a market, there may be no secondary market at all for the securities because it is likely that CGMI will be the only broker-dealer that is willing to buy your securities prior to maturity.  Accordingly, an investor must be prepared to hold the securities until maturity.

▪ The estimated value of the securities on the pricing date, based on CGMI’s proprietary pricing models and our internal funding rate, is less than the issue price.  The difference is attributable to certain costs associated with selling, structuring and hedging the securities that are included in the issue price.  These costs include (i) any selling concessions or other fees paid in connection with the offering of the securities, (ii) hedging and other costs incurred by us and our affiliates in connection with the offering of the securities and (iii) the expected profit (which may be more or less than actual profit) to CGMI or other of our affiliates in connection with hedging our obligations under the securities.  These costs adversely affect the economic terms of the securities because, if they were lower, the economic terms of the securities would be more favorable to you.  The economic terms of the securities are also likely to be adversely affected by the use of our internal funding rate, rather than our secondary market rate, to price the securities.  See “The estimated value of the securities would be lower if it were calculated based on our secondary market rate” below.

▪ The estimated value of the securities was determined for us by our affiliate using proprietary pricing models.  CGMI derived the estimated value disclosed on the cover page of this pricing supplement from its proprietary pricing models.  In doing so, it may have made discretionary judgments about the inputs to its models, such as the volatility of, and correlation between, the closing values of the underlyings, dividend yields on the underlyings and interest rates. CGMI’s views on these inputs may differ from your or others’ views, and as an underwriter in this offering, CGMI’s interests may conflict with yours.  Both the models and the inputs to the models may prove to be wrong and therefore not an accurate reflection of the value of the securities.  Moreover, the estimated value of the securities set forth on the cover page of this pricing supplement may differ from the value that we or our affiliates may determine for the securities for other purposes, including for accounting purposes.  You should not invest in the securities because of the estimated value of the securities.  Instead, you should be willing to hold the securities to maturity irrespective of the initial estimated value.

▪ The estimated value of the securities would be lower if it were calculated based on our secondary market rate.  The estimated value of the securities included in this pricing supplement is calculated based on our internal funding rate, which is the rate at which we are willing to borrow funds through the issuance of the securities. Our internal funding rate is generally lower than our secondary market rate, which is the rate that CGMI will use in determining the value of the securities for purposes of any purchases of the securities from you in the secondary market.  If the estimated value included in this pricing supplement were based on our secondary market rate, rather than our internal funding rate, it would likely be lower.  We determine our internal funding rate based on factors such as the costs associated with the securities, which are generally higher than the costs associated with conventional debt securities, and our liquidity needs and preferences.  Our internal funding rate is not an interest rate that is payable on the securities.

PS-8

Citigroup Global Markets Holdings Inc.

Because there is not an active market for traded instruments referencing our outstanding debt obligations, CGMI determines our secondary market rate based on the market price of traded instruments referencing the debt obligations of Citigroup Inc., our parent company and the guarantor of all payments due on the securities, but subject to adjustments that CGMI makes in its sole discretion.  As a result, our secondary market rate is not a market-determined measure of our creditworthiness, but rather reflects the market’s perception of our parent company’s creditworthiness as adjusted for discretionary factors such as CGMI’s preferences with respect to purchasing the securities prior to maturity.

▪ The estimated value of the securities is not an indication of the price, if any, at which CGMI or any other person may be willing to buy the securities from you in the secondary market.  Any such secondary market price will fluctuate over the term of the securities based on the market and other factors described in the next risk factor.  Moreover, unlike the estimated value included in this pricing supplement, any value of the securities determined for purposes of a secondary market transaction will be based on our secondary market rate, which will likely result in a lower value for the securities than if our internal funding rate were used.  In addition, any secondary market price for the securities will be reduced by a bid-ask spread, which may vary depending on the aggregate stated principal amount of the securities to be purchased in the secondary market transaction, and the expected cost of unwinding related hedging transactions.  As a result, it is likely that any secondary market price for the securities will be less than the issue price.

▪ The value of the securities prior to maturity will fluctuate based on many unpredictable factors. The value of your securities prior to maturity will fluctuate based on the closing values of the underlyings, the volatility of, and correlation between, the closing values of the underlyings, dividend yields on the underlyings, interest rates generally, the time remaining to maturity and our and Citigroup Inc.’s creditworthiness, as reflected in our secondary market rate, among other factors described under “Risk Factors Relating to the Securities—Risk Factors Relating to All Securities—The value of your securities prior to maturity will fluctuate based on many unpredictable factors” in the accompanying product supplement.  Changes in the closing values of the underlyings may not result in a comparable change in the value of your securities.  You should understand that the value of your securities at any time prior to maturity may be significantly less than the issue price.

▪ Immediately following issuance, any secondary market bid price provided by CGMI, and the value that will be indicated on any brokerage account statements prepared by CGMI or its affiliates, will reflect a temporary upward adjustment.  The amount of this temporary upward adjustment will steadily decline to zero over the temporary adjustment period.  See “Valuation of the Securities” in this pricing supplement.

▪ Our offering of the securities is not a recommendation of any underlying. The fact that we are offering the securities does not mean that we believe that investing in an instrument linked to the underlyings is likely to achieve favorable returns. In fact, as we are part of a global financial institution, our affiliates may have positions (including short positions) in the underlyings or in instruments related to the underlyings, and may publish research or express opinions, that in each case are inconsistent with an investment linked to the underlyings. These and other activities of our affiliates may affect the closing values of the underlyings in a way that negatively affects the value of and your return on the securities.

▪ The closing value of an underlying may be adversely affected by our or our affiliates’ hedging and other trading activities.  We have hedged our obligations under the securities through CGMI or other of our affiliates, who have taken positions in the underlyings or in financial instruments related to the underlyings and may adjust such positions during the term of the securities.  Our affiliates also take positions in the underlyings or in financial instruments related to the underlyings on a regular basis (taking long or short positions or both), for their accounts, for other accounts under their management or to facilitate transactions on behalf of customers. These activities could affect the closing values of the underlyings in a way that negatively affects the value of and your return on the securities. They could also result in substantial returns for us or our affiliates while the value of the securities declines.

▪ We and our affiliates may have economic interests that are adverse to yours as a result of our affiliates’ business activities. Our affiliates engage in business activities with a wide range of companies.  These activities include extending loans, making and facilitating investments, underwriting securities offerings and providing advisory services.  These activities could involve or affect the underlyings in a way that negatively affects the value of and your return on the securities. They could also result in substantial returns for us or our affiliates while the value of the securities declines.  In addition, in the course of this business, we or our affiliates may acquire non-public information, which will not be disclosed to you.

▪ The calculation agent, which is an affiliate of ours, will make important determinations with respect to the securities.  If certain events occur during the term of the securities, such as market disruption events and other events with respect to an underlying, CGMI, as calculation agent, will be required to make discretionary judgments that could significantly affect your return on the securities.  In making these judgments, the calculation agent’s interests as an affiliate of ours could be adverse to your interests as a holder of the securities.  See “Risk Factors Relating to the Securities—Risk Factors Relating to All Securities—The calculation agent, which is an affiliate of ours, will make important determinations with respect to the securities” in the accompanying product supplement.

PS-9

Citigroup Global Markets Holdings Inc.

▪ Changes that affect the underlyings may affect the value of your securities.  The sponsors of the underlyings may at any time make methodological changes or other changes in the manner in which they operate that could affect the values of the underlyings.  We are not affiliated with any such underlying sponsor and, accordingly, we have no control over any changes any such sponsor may make.  Such changes could adversely affect the performance of the underlyings and the value of and your return on the securities.

▪ The U.S. federal tax consequences of an investment in the securities are unclear.  There is no direct legal authority regarding the proper U.S. federal tax treatment of the securities, and we do not plan to request a ruling from the Internal Revenue Service (the “IRS”).  Consequently, significant aspects of the tax treatment of the securities are uncertain, and the IRS or a court might not agree with the treatment of the securities as prepaid forward contracts.  If the IRS were successful in asserting an alternative treatment of the securities, the tax consequences of the ownership and disposition of the securities might be materially and adversely affected.  Moreover, future legislation, Treasury regulations or IRS guidance could adversely affect the U.S. federal tax treatment of the securities, possibly retroactively.

If you are a non-U.S. investor, you should review the discussion of withholding tax issues in “United States Federal Tax Considerations—Non-U.S. Holders” below.

You should read carefully the discussion under “United States Federal Tax Considerations” and “Risk Factors Relating to the Securities” in the accompanying product supplement and “United States Federal Tax Considerations” in this pricing supplement.  You should also consult your tax adviser regarding the U.S. federal tax consequences of an investment in the securities, as well as tax consequences arising under the laws of any state, local or non-U.S. taxing jurisdiction.

PS-10

Citigroup Global Markets Holdings Inc.

Information About the Nasdaq-100 Index^®

The Nasdaq-100 Index^® is a modified market capitalization-weighted index of stocks of the 100 largest non-financial companies listed on the Nasdaq Stock Market. All stocks included in the Nasdaq-100 Index^® are traded on a major U.S. exchange. The Nasdaq-100 Index^® was developed by the Nasdaq Stock Market, Inc. and is calculated, maintained and published by Nasdaq, Inc.

Please refer to the section “Equity Index Descriptions—The Nasdaq-100 Index^®” in the accompanying underlying supplement for additional information.

We have derived all information regarding the Nasdaq-100 Index^® from publicly available information and have not independently verified any information regarding the Nasdaq-100 Index^®. This pricing supplement relates only to the securities and not to the Nasdaq-100 Index^®. We make no representation as to the performance of the Nasdaq-100 Index^® over the term of the securities.

The securities represent obligations of Citigroup Global Markets Holdings Inc. (guaranteed by Citigroup Inc.) only. The sponsor of the Nasdaq-100 Index^® is not involved in any way in this offering and has no obligation relating to the securities or to holders of the securities.

Historical Information

The closing value of the Nasdaq-100 Index^® on June 30, 2025 was 22,679.01.

The graph below shows the closing value of the Nasdaq-100 Index^®  for each day such value was available from January 2, 2015 to June 30, 2025.  We obtained the closing values from Bloomberg L.P., without independent verification. You should not take the historical closing values as an indication of future performance.

Nasdaq-100 Index^® – Historical Closing Values

January 2, 2015 to June 30, 2025

PS-11

Citigroup Global Markets Holdings Inc.

Information About the S&P 500^® Index

The S&P 500^® Index consists of the common stocks of 500 issuers selected to provide a performance benchmark for the large capitalization segment of the U.S. equity markets. It is calculated and maintained by S&P Dow Jones Indices LLC.

Please refer to the section “Equity Index Descriptions—The S&P U.S. Indices” in the accompanying underlying supplement for additional information.

We have derived all information regarding the S&P 500^® Index from publicly available information and have not independently verified any information regarding the S&P 500^® Index.  This pricing supplement relates only to the securities and not to the S&P 500^® Index.  We make no representation as to the performance of the S&P 500^® Index over the term of the securities.

The securities represent obligations of Citigroup Global Markets Holdings Inc. (guaranteed by Citigroup Inc.) only.  The sponsor of the S&P 500^® Index is not involved in any way in this offering and has no obligation relating to the securities or to holders of the securities.

Historical Information

The closing value of the S&P 500^® Index on June 30, 2025 was 6,204.95.

The graph below shows the closing value of the S&P 500^® Index for each day such value was available from January 2, 2015 to June 30, 2025. We obtained the closing values from Bloomberg L.P., without independent verification. You should not take the historical closing values as an indication of future performance.

S&P 500^® Index – Historical Closing Values

January 2, 2015 to June 30, 2025

PS-12

Citigroup Global Markets Holdings Inc.

United States Federal Tax Considerations

You should read carefully the discussion under “United States Federal Tax Considerations” and “Risk Factors Relating to the Securities” in the accompanying product supplement and “Summary Risk Factors” in this pricing supplement.  

In the opinion of our counsel, Davis Polk & Wardwell LLP, which is based on current market conditions, a security should be treated as a prepaid forward contract for U.S. federal income tax purposes.  By purchasing a security, you agree (in the absence of an administrative determination or judicial ruling to the contrary) to this treatment.  There is uncertainty regarding this treatment, and the IRS or a court might not agree with it.

Assuming this treatment of the securities is respected and subject to the discussion in “United States Federal Tax Considerations” in the accompanying product supplement, the following U.S. federal income tax consequences should result under current law:

· You should not recognize taxable income over the term of the securities prior to maturity, other than pursuant to a sale or exchange.

· Upon a sale or exchange of a security (including retirement at maturity), you should recognize capital gain or loss equal to the difference between the amount realized and your tax basis in the security.  Such gain or loss should be long-term capital gain or loss if you held the security for more than one year.

We do not plan to request a ruling from the IRS regarding the treatment of the securities. An alternative characterization of the securities could materially and adversely affect the tax consequences of ownership and disposition of the securities, including the timing and character of income recognized. In addition, the U.S. Treasury Department and the IRS have requested comments on various issues regarding the U.S. federal income tax treatment of “prepaid forward contracts” and similar financial instruments and have indicated that such transactions may be the subject of future regulations or other guidance. Furthermore, members of Congress have proposed legislative changes to the tax treatment of derivative contracts. Any legislation, Treasury regulations or other guidance promulgated after consideration of these issues could materially and adversely affect the tax consequences of an investment in the securities, possibly with retroactive effect. You should consult your tax adviser regarding possible alternative tax treatments of the securities and potential changes in applicable law.

Non-U.S. Holders. Subject to the discussions below and in “United States Federal Tax Considerations” in the accompanying product supplement, if you are a Non-U.S. Holder (as defined in the accompanying product supplement) of the securities, you generally should not be subject to U.S. federal withholding or income tax in respect of any amount paid to you with respect to the securities, provided that (i) income in respect of the securities is not effectively connected with your conduct of a trade or business in the United States, and (ii) you comply with the applicable certification requirements.

As discussed under “United States Federal Tax Considerations—Tax Consequences to Non-U.S. Holders” in the accompanying product supplement, Section 871(m) of the Code and Treasury regulations promulgated thereunder (“Section 871(m)”) generally impose a 30% withholding tax on dividend equivalents paid or deemed paid to Non-U.S. Holders with respect to certain financial instruments linked to U.S. equities (“U.S. Underlying Equities”) or indices that include U.S. Underlying Equities.  Section 871(m) generally applies to instruments that substantially replicate the economic performance of one or more U.S. Underlying Equities, as determined based on tests set forth in the applicable Treasury regulations.  However, the regulations, as modified by an IRS notice, exempt financial instruments issued prior to January 1, 2027 that do not have a “delta” of one.  Based on the terms of the securities and representations provided by us, our counsel is of the opinion that the securities should not be treated as transactions that have a “delta” of one within the meaning of the regulations with respect to any U.S. Underlying Equity and, therefore, should not be subject to withholding tax under Section 871(m).

A determination that the securities are not subject to Section 871(m) is not binding on the IRS, and the IRS may disagree with this treatment.  Moreover, Section 871(m) is complex and its application may depend on your particular circumstances, including your other transactions.  You should consult your tax adviser regarding the potential application of Section 871(m) to the securities.

If withholding tax applies to the securities, we will not be required to pay any additional amounts with respect to amounts withheld.

You should read the section entitled “United States Federal Tax Considerations” in the accompanying product supplement.  The preceding discussion, when read in combination with that section, constitutes the full opinion of Davis Polk & Wardwell LLP regarding the material U.S. federal tax consequences of owning and disposing of the securities.  

You should also consult your tax adviser regarding all aspects of the U.S. federal income and estate tax consequences of an investment in the securities and any tax consequences arising under the laws of any state, local or non-U.S. taxing jurisdiction.

PS-13

Citigroup Global Markets Holdings Inc.

Supplemental Plan of Distribution

CGMI, an affiliate of Citigroup Global Markets Holdings Inc. and the underwriter of the sale of the securities, is acting as principal and will receive an underwriting fee of up to $10.00 for each security sold in this offering. The actual underwriting fee will be equal to the selling concession provided to selected dealers, as described in this paragraph. From this underwriting fee, CGMI will pay selected dealers not affiliated with CGMI a variable selling concession of up to $10.00 for each security they sell. For the avoidance of doubt, the fees and selling concessions described in this pricing supplement will not be rebated if the securities are automatically redeemed prior to maturity.

See “Plan of Distribution; Conflicts of Interest” in the accompanying product supplement and “Plan of Distribution” in each of the accompanying prospectus supplement and prospectus for additional information.

Valuation of the Securities

CGMI calculated the estimated value of the securities set forth on the cover page of this pricing supplement based on proprietary pricing models. CGMI’s proprietary pricing models generated an estimated value for the securities by estimating the value of a hypothetical package of financial instruments that would replicate the payout on the securities, which consists of a fixed-income bond (the “bond component”) and one or more derivative instruments underlying the economic terms of the securities (the “derivative component”). CGMI calculated the estimated value of the bond component using a discount rate based on our internal funding rate. CGMI calculated the estimated value of the derivative component based on a proprietary derivative-pricing model, which generated a theoretical price for the instruments that constitute the derivative component based on various inputs, including the factors described under “Summary Risk Factors—The value of the securities prior to maturity will fluctuate based on many unpredictable factors” in this pricing supplement, but not including our or Citigroup Inc.’s creditworthiness. These inputs may be market-observable or may be based on assumptions made by CGMI in its discretionary judgment.

For a period of approximately three months following issuance of the securities, the price, if any, at which CGMI would be willing to buy the securities from investors, and the value that will be indicated for the securities on any brokerage account statements prepared by CGMI or its affiliates (which value CGMI may also publish through one or more financial information vendors), will reflect a temporary upward adjustment from the price or value that would otherwise be determined. This temporary upward adjustment represents a portion of the hedging profit expected to be realized by CGMI or its affiliates over the term of the securities. The amount of this temporary upward adjustment will decline to zero on a straight-line basis over the three-month temporary adjustment period. However, CGMI is not obligated to buy the securities from investors at any time.  See “Summary Risk Factors—The securities will not be listed on any securities exchange and you may not be able to sell them prior to maturity.”

Validity of the Securities

In the opinion of Davis Polk & Wardwell LLP, as special products counsel to Citigroup Global Markets Holdings Inc., when the securities offered by this pricing supplement have been executed and issued by Citigroup Global Markets Holdings Inc. and authenticated by the trustee pursuant to the indenture, and delivered against payment therefor, such securities and the related guarantee of Citigroup Inc. will be valid and binding obligations of Citigroup Global Markets Holdings Inc. and Citigroup Inc., respectively, enforceable in accordance with their respective terms, subject to applicable bankruptcy, insolvency and similar laws affecting creditors’ rights generally, concepts of reasonableness and equitable principles of general applicability (including, without limitation, concepts of good faith, fair dealing and the lack of bad faith), provided that such counsel expresses no opinion as to the effect of fraudulent conveyance, fraudulent transfer or similar provision of applicable law on the conclusions expressed above. This opinion is given as of the date of this pricing supplement and is limited to the laws of the State of New York, except that such counsel expresses no opinion as to the application of state securities or Blue Sky laws to the securities.

In giving this opinion, Davis Polk & Wardwell LLP has assumed the legal conclusions expressed in the opinions set forth below of Alexia Breuvart, Secretary and General Counsel of Citigroup Global Markets Holdings Inc., and Karen Wang, Senior Vice President – Corporate Securities Issuance Legal of Citigroup Inc.  In addition, this opinion is subject to the assumptions set forth in the letter of Davis Polk & Wardwell LLP dated February 14, 2024, which has been filed as an exhibit to a Current Report on Form 8-K filed by Citigroup Inc. on February 14, 2024, that the indenture has been duly authorized, executed and delivered by, and is a valid, binding and enforceable agreement of, the trustee and that none of the terms of the securities nor the issuance and delivery of the securities and the related guarantee, nor the compliance by Citigroup Global Markets Holdings Inc. and Citigroup Inc. with the terms of the securities and the related guarantee respectively, will result in a violation of any provision of any instrument or agreement then binding upon Citigroup Global Markets Holdings Inc. or Citigroup Inc., as applicable, or any restriction imposed by any court or governmental body having jurisdiction over Citigroup Global Markets Holdings Inc. or Citigroup Inc., as applicable.

In the opinion of Alexia Breuvart, Secretary and General Counsel of Citigroup Global Markets Holdings Inc., (i) the terms of the securities offered by this pricing supplement have been duly established under the indenture and the Board of Directors (or a duly authorized committee thereof) of Citigroup Global Markets Holdings Inc. has duly authorized the issuance and sale of such securities and such authorization has not been modified or rescinded; (ii) Citigroup Global Markets Holdings Inc. is validly existing and in good standing under the laws of the State of New York; (iii) the indenture has been duly authorized, executed and delivered by Citigroup Global Markets Holdings Inc.; and (iv) the execution and delivery of such indenture and of the securities offered by this pricing supplement by Citigroup Global Markets Holdings Inc., and the performance by Citigroup Global Markets Holdings Inc. of its obligations thereunder, are within its corporate powers and do not contravene its certificate of incorporation or bylaws or other constitutive documents. This opinion is given as of the date of this pricing supplement and is limited to the laws of the State of New York.

PS-14

Citigroup Global Markets Holdings Inc.

Alexia Breuvart, or other internal attorneys with whom she has consulted, has examined and is familiar with originals, or copies certified or otherwise identified to her satisfaction, of such corporate records of Citigroup Global Markets Holdings Inc., certificates or documents as she has deemed appropriate as a basis for the opinions expressed above. In such examination, she or such persons has assumed the legal capacity of all natural persons, the genuineness of all signatures (other than those of officers of Citigroup Global Markets Holdings Inc.), the authenticity of all documents submitted to her or such persons as originals, the conformity to original documents of all documents submitted to her or such persons as certified or photostatic copies and the authenticity of the originals of such copies.

In the opinion of Karen Wang, Senior Vice President – Corporate Securities Issuance Legal of Citigroup Inc., (i) the Board of Directors (or a duly authorized committee thereof) of Citigroup Inc. has duly authorized the guarantee of such securities by Citigroup Inc. and such authorization has not been modified or rescinded; (ii) Citigroup Inc. is validly existing and in good standing under the laws of the State of Delaware; (iii) the indenture has been duly authorized, executed and delivered by Citigroup Inc.; and (iv) the execution and delivery of such indenture, and the performance by Citigroup Inc. of its obligations thereunder, are within its corporate powers and do not contravene its certificate of incorporation or bylaws or other constitutive documents.  This opinion is given as of the date of this pricing supplement and is limited to the General Corporation Law of the State of Delaware.

Karen Wang, or other internal attorneys with whom she has consulted, has examined and is familiar with originals, or copies certified or otherwise identified to her satisfaction, of such corporate records of Citigroup Inc., certificates or documents as she has deemed appropriate as a basis for the opinions expressed above. In such examination, she or such persons has assumed the legal capacity of all natural persons, the genuineness of all signatures (other than those of officers of Citigroup Inc.), the authenticity of all documents submitted to her or such persons as originals, the conformity to original documents of all documents submitted to her or such persons as certified or photostatic copies and the authenticity of the originals of such copies.

Contact

Clients may contact their local brokerage representative. Third-party distributors may contact Citi Structured Investment Sales at (212)

723-7005.

© 2025 Citigroup Global Markets Inc. All rights reserved. Citi and Citi and Arc Design are trademarks and service marks of Citigroup Inc. or its affiliates and are used and registered throughout the world.

PS-15

FAQ

What upside can investors earn on Morgan Stanley (MS) 133 % Market-Linked Notes?

At maturity holders receive 133 % of any positive change in the S&P 500 Futures Excess Return Index, plus return of principal.

Is principal protected on the MS Structured Notes due 5 July 2030?

Yes. Investors receive at least the $1,000 principal per note at maturity, subject to Morgan Stanley’s credit risk.

Why is the estimated value ($966.60) below the $1,000 issue price?

The gap reflects issuance, structuring, hedging costs and Morgan Stanley’s internal funding rate, all borne by investors.

Can I sell the notes before maturity?

MS & Co. may make a market but is not obligated; the notes are unlisted and may trade at a substantial discount.

How are the notes taxed for U.S. investors?

They are treated as contingent payment debt instruments; holders must accrue OID at a 4.5259 % comparable yield each year.

What index underlies the notes and does it include dividends?

The notes track the S&P 500 Futures Excess Return Index, which excludes dividend income, unlike the S&P 500 total-return index.