[SCHEDULE 13G] MARKETAXESS HOLDINGS INC Passive Investment Disclosure (>5%)

Rhea-AI Filing Summary

MarketAxess Holdings Inc reported that Vanguard Portfolio Management beneficially owned 2,168,085 shares of Common Stock, representing 6.09% of the class as of 03/31/2026. The filing states Vanguard Portfolio Management has sole dispositive power over 2,168,085 shares and sole voting power for 4,414 shares. The filing explains these holdings include securities held by Vanguard funds and certain affiliates over which Vanguard exercises dispositive authority.

Insights

Institutional Ownership Analyst

Vanguard holds a meaningful passive stake in MarketAxess at 6.09% as of 03/31/2026.

Vanguard Portfolio Management reports beneficial ownership of 2,168,085 shares, with sole dispositive power over that amount and limited sole voting power of 4,414 shares. This structure is typical for asset managers operating across fund sleeves.

Cash‑flow treatment and trading intent are not stated; subsequent filings or fund disclosures would clarify whether this position is passive or part of dynamic allocation strategies.

Regulatory Compliance Specialist

The Schedule 13G disclosure follows passive investor reporting conventions and includes affiliate attribution language.

The filing cites SEC Release No. 34‑39538 and lists affiliated entities (Vanguard Fiduciary Trust Company, Vanguard Global Advisers, LLC) whose holdings are included. It identifies the filer’s address and the reporting officer signature dated 04/29/2026.

Investors should reference future amendments (Schedule 13D/13G updates) if ownership or voting arrangements change.

Key Figures

Shares beneficially owned: 2,168,085 shares Percent of class: 6.09% Sole voting power: 4,414 shares +2 more

5 metrics

Shares beneficially owned 2,168,085 shares beneficial ownership reported as of 03/31/2026

Percent of class 6.09% ownership percentage of Common Stock

Sole voting power 4,414 shares shares for which filer has sole power to vote

Sole dispositive power 2,168,085 shares shares for which filer has sole power to dispose

Signature date 04/29/2026 Schedule 13G signed by reporting officer

Key Terms

Schedule 13G, Beneficially owned, Dispositive power, SEC Release No. 34-39538

4 terms

Schedule 13G regulatory

"Name of form: SCHEDULE 13G (reporting passive beneficial ownership)"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

Beneficially owned financial

"Amount beneficially owned: 2168085 (describes economic interest)"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

Dispositive power regulatory

"Sole power to dispose or to direct the disposition of: 2168085"

Dispositive power is the authority to decide the final outcome of an asset, legal claim, contract, or corporate action — in effect the power to dispose of or resolve something. For investors it matters because whoever holds that authority can determine who gets paid, who controls an asset or vote, and how risks and returns are allocated; think of it like holding the key that lets you lock in the winner or loser in a deal.

SEC Release No. 34-39538 regulatory

"In accordance with SEC Release No. 34-39538 (January 12, 1998) (affiliate attribution)"

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Accepted by SEC EDGAR 04/29/2026 - 02:14 PM Learn about SEC filing dates

FAQ

How many MarketAxess (MKTX) shares does Vanguard Portfolio Management report owning?

Vanguard Portfolio Management reports owning 2,168,085 shares of MarketAxess Common Stock. The filing shows this equals 6.09% of the class as reported on 03/31/2026.

What voting and dispositive powers does Vanguard report for MKTX holdings?

Vanguard reports sole dispositive power over 2,168,085 shares and sole voting power for 4,414 shares. Shared voting and dispositive powers are reported as 0 in the filing.

Which Vanguard entities are included in the beneficial‑ownership statement?

The filing states holdings include securities held by Vanguard funds and affiliates, including Vanguard Fiduciary Trust Company and Vanguard Global Advisers, LLC, under SEC Release No. 34‑39538.

What date is the beneficial‑ownership percentage based on?

The ownership percentage (6.09%) is reported with an as of date of 03/31/2026, as shown near the cover information in the filing.

Who signed the Schedule 13G for Vanguard Portfolio Management?

The Schedule 13G is signed by Ashley Grim, Head of Global Fund Administration, with a signature date of 04/29/2026, as provided in the filing.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

MarketAxess Holdings Inc

(Name of Issuer)

Common Stock

(Title of Class of Securities)

57060D108

(CUSIP Number)

03/31/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 57060D108

1

Names of Reporting Persons

Vanguard Portfolio Management

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

PENNSYLVANIA

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 4,414.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 2,168,085.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,168,085.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

6.09 %

12

Type of Reporting Person (See Instructions)

IA

Comment for Type of Reporting Person: In accordance with SEC Release No. 34-39538 (January 12, 1998), this Schedule 13G reflects the securities beneficially owned, or deemed to be beneficially owned, by Vanguard Portfolio Management LLC and the following affiliates of Vanguard Portfolio Management LLC or business divisions of such affiliates: Vanguard Fiduciary Trust Company and Vanguard Global Advisers, LLC. This Schedule 13G includes securities held by Vanguard funds, or sleeves thereof, over which Vanguard Portfolio Management LLC exercises dispositive power, in addition to securities held by clients over which the affiliates or business divisions of such affiliates indicated above exercise dispositive and/or voting power. This Schedule 13G does not include securities, if any, beneficially owned by other subsidiaries or affiliates of Vanguard Portfolio Management LLC, or business divisions of such subsidiaries whose ownership of securities is disaggregated from that of the reporting business unit in accordance with such release.

SCHEDULE 13G

Item 1.
(a)	Name of issuer: MarketAxess Holdings Inc
(b)	Address of issuer's principal executive offices: 299 Park Avenue, 10th Floor, New York, NY, 10171
Item 2.
(a)	Name of person filing: Vanguard Portfolio Management
(b)	Address or principal business office or, if none, residence: 100 Vanguard Blvd,, Malvern, PA, 19355
(c)	Citizenship: PA
(d)	Title of class of securities: Common Stock
(e)	CUSIP Number(s): 57060D108
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 2168085
(b)	Percent of class: 6.09 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 4414
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 2168085
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. Vanguard Portfolio Management, including investment companies registered under the Investment Company Act of 1940 and other managed accounts, have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the securities reported herein.No one other person's interest in the securities reported herein is more than 5%.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Vanguard Portfolio Management

Signature:	Ashley Grim
Name/Title:	Head of Global Fund Administration
Date:	04/29/2026