NB Bancorp director reports tax share withholding

NB Bancorp, Inc. director Kenneth C. Montgomery reported a tax-withholding disposition of 5,015 shares of common stock at $19.82 per share on April 24, 2026.

Rhea-AI Filing Summary

NB Bancorp, Inc. director Kenneth C. Montgomery reported a tax-withholding disposition of 5,015 shares of common stock at $19.82 per share on April 24, 2026. The shares were delivered to cover tax obligations related to equity awards rather than sold in the open market.

After this transaction, Montgomery directly holds 80,125 shares, including restricted stock that vests 100% on January 2, 2027 and additional restricted shares vesting 20% per year starting April 24, 2026.

Insider Trade Summary

Exercise Price or Tax Liability: 5,015 shares

Exercise Price or Tax Liability 1 txn

Insider Montgomery Kenneth C.

Role Director

Type	Security	Shares	Price	Value
Exercise Price or Tax Liability	Common Stock	5,015	$19.82	$99K

Holdings After Transaction: Common Stock — 80,125 shares (Direct)

Footnotes (2)

1. F1. Shares of restricted stock vest 100% on January 2, 2027.
2. F2. Includes shares of restricted stock which vest at a rate of 20% per year commencing on April 24, 2026.

Key Figures

Tax-withholding shares: 5,015 shares Price per share: $19.82 per share Shares held after transaction: 80,125 shares

3 metrics

Tax-withholding shares 5,015 shares Common stock delivered for tax-withholding disposition on April 24, 2026

Price per share $19.82 per share Value assigned to shares used for tax-withholding disposition

Shares held after transaction 80,125 shares Direct ownership by Kenneth C. Montgomery following the Form 4 transaction

Key Terms

tax-withholding disposition, restricted stock, vest at a rate of 20% per year

3 terms

tax-withholding disposition financial

"The filing characterizes the event as a tax-withholding disposition coded “F”."

A tax-withholding disposition is an event or transaction—such as selling or transferring securities, exercising options, or receiving compensation—that triggers a requirement to hold back part of the payment and remit it to tax authorities. It matters to investors because it reduces the cash they receive immediately and can change the timing and amount of taxable income, like a cashier taking a portion of your sale proceeds to pay taxes before you get the rest.

restricted stock financial

"Shares of restricted stock vest 100% on January 2, 2027."

Shares granted to an individual that carry limits on transfer or sale until certain conditions are met, such as staying with the company for a set time or hitting performance targets. Think of them as a locked gift that gradually opens; for investors they matter because they affect how many shares may enter the market later, signal management incentives and potential dilution, and reveal confidence in future company performance.

vest at a rate of 20% per year financial

"Includes shares of restricted stock which vest at a rate of 20% per year commencing on April 24, 2026."

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What insider transaction did NB Bancorp (NBBK) disclose for Kenneth C. Montgomery?

NB Bancorp reported that director Kenneth C. Montgomery had 5,015 common shares withheld at $19.82 per share. This was a tax-withholding disposition, where shares are delivered to satisfy tax obligations tied to equity compensation awards rather than sold in the market.

How many NB Bancorp (NBBK) shares were involved in the tax-withholding event?

The filing shows 5,015 NB Bancorp common shares were used for a tax-withholding disposition at $19.82 per share. This reflects shares delivered to cover tax liabilities associated with equity awards, not an open-market sale initiated for portfolio or valuation reasons.

How many NB Bancorp (NBBK) shares does Kenneth C. Montgomery own after this Form 4?

Following the tax-withholding disposition, Kenneth C. Montgomery directly holds 80,125 NB Bancorp common shares. This total includes restricted stock that vests over time according to the schedules disclosed, indicating a continuing equity stake after the routine tax-related transaction.

What are the restricted stock vesting terms for the NB Bancorp (NBBK) director?

One block of restricted stock vests 100% on January 2, 2027. Additional restricted shares vest at 20% per year starting April 24, 2026. These schedules describe when the director’s unvested equity awards incrementally become fully owned and no longer subject to forfeiture conditions.

Does the NB Bancorp (NBBK) Form 4 indicate an open-market sale by the director?

No, the Form 4 describes a tax-withholding disposition coded as “F,” not an open-market sale. Shares were delivered at $19.82 per share to satisfy tax obligations on equity awards, a mechanical step that doesn’t reflect an active decision to sell shares in the market.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 04/27/2026 - 02:48 PM EDT Learn about SEC filing dates

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Montgomery Kenneth C.

(Last) (First) (Middle)

1063 GREAT PLAIN AVE

(Street)

NEEDHAM MASSACHUSETTS 02492

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
NB Bancorp, Inc. [ NBBK ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
04/24/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	04/24/2026		F		5,015	D	$19.82	80,125(1)(2)	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Shares of restricted stock vest 100% on January 2, 2027.

2. Includes shares of restricted stock which vest at a rate of 20% per year commencing on April 24, 2026.

	/s/ Steven Lanter, pursuant to power of attorney	04/27/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)