NB Bancorp director updates Form 4 holdings

NB Bancorp, Inc. director Mark Whalen filed an amended Form 4 that updates his reported holdings without showing any new buy or sell transactions.

Rhea-AI Filing Summary

NB Bancorp, Inc. director Mark Whalen filed an amended Form 4 that updates his reported holdings without showing any new buy or sell transactions. The filing reports 77,639 shares of common stock held directly and 30,000 shares held indirectly as trustee for a trust.

Footnotes explain that the direct holdings include restricted stock that vests 20% per year starting on April 24, 2026 and additional restricted stock vesting 100% on January 2, 2027. The amendment corrects a previously filed Form 4 that had mistakenly reported a disposition of common shares that did not actually occur.

Insider Trade Summary

2 transactions reported

Mixed 2 txns

Insider Whalen Mark

Role Director

Type	Security	Shares	Price	Value
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 77,639 shares (Direct); Common Stock — 30,000 shares (Indirect, As trustee for trust)

Footnotes (3)

1. F1. Includes shares of restricted stock which vest at a rate of 20% per year commencing on April 24, 2026.
2. F2. Includes shares of restricted stock which vest 100% on January 2, 2027.
3. F3. On April 27, 2026, a Form 4 was mistakenly filed reporting a disposition of shares of common stock that did not in fact occur. The change in the securities beneficially owned has been corrected accordingly in this amended Form 4.

Key Figures

Direct common shares: 77,639 shares Indirect common shares (trustee): 30,000 shares Vesting start (20% per year): April 24, 2026 +2 more

5 metrics

Direct common shares 77,639 shares Total common stock held directly after amendment

Indirect common shares (trustee) 30,000 shares Common stock held indirectly as trustee for a trust

Vesting start (20% per year) April 24, 2026 Restricted stock vests 20% annually beginning on this date

Cliff vesting date January 2, 2027 Restricted stock vests 100% on this date

Unknown transaction entries 2 entries Both coded as holding entries with unknown transaction code

Key Terms

restricted stock, beneficially owned, trustee, Form 4, +1 more

5 terms

restricted stock financial

"Includes shares of restricted stock which vest at a rate of 20% per year"

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.

beneficially owned financial

"The change in the securities beneficially owned has been corrected accordingly"

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.

trustee financial

"As trustee for trust"

A trustee is a person or institution legally appointed to hold and manage assets or enforce an agreement on behalf of other people (beneficiaries). Think of a trustee as a neutral referee or custodian who must act in the beneficiaries’ best interests, follow the trust or contract rules, and handle distributions, recordkeeping and enforcement. Investors care because a trustworthy trustee protects their rights, ensures promised payments or remedies are delivered, and can influence recoveries if things go wrong.

Form 4 regulatory

"On April 27, 2026, a Form 4 was mistakenly filed reporting a disposition"

Form 4 is a official document that company insiders, such as executives or major shareholders, file with regulators whenever they buy or sell company shares. It provides transparency about how those with inside knowledge are trading, helping investors see if insiders are confident in the company's prospects or may be selling for personal reasons. This information can influence investor decisions by revealing insiders' perspectives on the company's value.

disposition financial

"reporting a disposition of shares of common stock that did not in fact occur"

FAQ

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

What does Mark Whalen’s amended Form 4 for NB Bancorp (NBBK) show?

The amended Form 4 updates Mark Whalen’s reported holdings with no new trades. It shows 77,639 NB Bancorp common shares held directly and 30,000 shares held indirectly as trustee, plus notes on restricted stock vesting schedules.

Did Mark Whalen buy or sell NB Bancorp (NBBK) shares in this Form 4/A?

No, the Form 4/A does not report any new purchases or sales. It only amends prior disclosure, correcting an earlier Form 4 that mistakenly showed a disposition of NB Bancorp common stock that never occurred.

How many NB Bancorp (NBBK) shares does Mark Whalen now report owning?

He reports 77,639 NB Bancorp common shares held directly and 30,000 shares held indirectly as trustee. These totals include restricted stock awards that vest over time, as detailed in the filing’s footnotes.

What restricted stock vesting terms are disclosed for NB Bancorp (NBBK) director Mark Whalen?

The filing notes restricted stock that vests 20% per year starting April 24, 2026. It also includes restricted shares vesting 100% on January 2, 2027, both forming part of Whalen’s reported NB Bancorp equity holdings.

Why was this NB Bancorp (NBBK) Form 4/A amendment necessary?

The amendment corrects an error from an April 27, 2026 Form 4. That earlier filing mistakenly reported a disposition of NB Bancorp common shares that did not actually occur, so this Form 4/A updates the beneficial ownership totals.

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

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Accepted by SEC EDGAR 05/15/2026 - 11:10 AM 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^*

Whalen Mark

(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)
04/27/2026

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								77,639(1)(2)(3)	D
Common Stock								30,000	I	As trustee for trust

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

2. Includes shares of restricted stock which vest 100% on January 2, 2027.

3. On April 27, 2026, a Form 4 was mistakenly filed reporting a disposition of shares of common stock that did not in fact occur. The change in the securities beneficially owned has been corrected accordingly in this amended Form 4.

	/s/ Steven T. Lanter, pursuant to power of attorney	05/15/2026
	** 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)