[Form 4] NB Bancorp, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Christopher R. Lynch, a director of NB Bancorp, Inc. (NBBK), reported an insider transaction dated 09/16/2025. The filing shows a sale of 600 shares of common stock for $0 (reported price $0), leaving Mr. Lynch with 92,562 shares held directly and an additional 60,000 shares held indirectly through an IRA. The filing notes 60,000 IRA holdings and that included restricted shares vest at 20% per year beginning April 24, 2026. The Form 4 was signed under power of attorney on 09/18/2025.

Positive

• Substantial retained ownership: Mr. Lynch retains 92,562 shares directly and 60,000 shares indirectly via an IRA, indicating continued insider alignment.
• Transparent vesting disclosure: The filing specifies restricted shares vest at 20% per year starting April 24, 2026, clarifying future share availability.

Negative

• Reported transaction price unclear: The sale of 600 shares is reported with a price of $0, providing no proceeds information in this filing.
• Small disposal recorded: A disposition of 600 shares was executed on 09/16/2025, which modestly reduces direct holdings.

Insights

Corporate Governance Expert

TL;DR: Director sold a small number of shares and retains substantial direct and IRA holdings; restricted shares vest beginning April 2026.

The 600-share disposition reported at a $0 price is small relative to the director's total direct shareholding of 92,562 and indirect IRA holding of 60,000, indicating no material change to ownership stakes. The disclosure that restricted stock vests 20% annually starting April 24, 2026 is governance-relevant for future insider liquidity and alignment with shareholders. The $0 price reporting should be interpreted strictly as reported on the form; no additional context or proceeds are provided in the filing.

Securities Analyst

TL;DR: Transaction is routine and immaterial to overall ownership; monitor vesting schedule for future sellable shares.

The disposal of 600 shares on 09/16/2025 represents a de minimis change versus the reported 152,562 total beneficial shares (direct plus IRA). The presence of restricted stock vesting 20% per year from April 24, 2026 signals staged future increases in liquid insider supply but does not itself indicate immediate dilution or material liquidity events. The filing lacks price/proceeds context beyond a $0 price entry, so financial implications are unclear from this document alone.

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

1. Name and Address of Reporting Person^*

Lynch Christopher R.

(Last) (First) (Middle)

1063 GREAT PLAIN AVE

(Street)

NEEDHAM MA 02492

(City) (State) (Zip)

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)

3. Date of Earliest Transaction (Month/Day/Year)
09/16/2025

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

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

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

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	09/16/2025		G		600	D	$0	92,562(1)	D
Common Stock								60,000	I	By IRA

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.

	/s/ Steven Lanter, pursuant to power of attorney	09/18/2025
	** 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.

FAQ

What insider transaction did Christopher R. Lynch report for NBBK?

The Form 4 reports a disposition of 600 common shares on 09/16/2025.

How many NBBK shares does Christopher R. Lynch beneficially own after the transaction?

He beneficially owns 92,562 shares directly and 60,000 shares indirectly through an IRA.

When do the restricted shares reported in the Form 4 vest?

Restricted shares vest at a rate of 20% per year commencing on April 24, 2026.

What price was reported for the 600-share disposition?

The filing reports a price of $0 for the 600-share disposition; no proceeds or additional price context is provided.

Who signed the Form 4 and when was it filed?

The Form 4 was signed by /s/ Steven Lanter, pursuant to power of attorney on 09/18/2025.