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

Rhea-AI Filing Summary

Darcey William, a director of NB Bancorp, Inc. (NBBK), reported purchases of company common stock executed on 08/11/2025. The filing shows a purchase of 4,861 shares at $17.30 and a separate purchase of 139 shares at $17.29. The report lists beneficial ownership following those transactions as 80,237 and 75,376 shares respectively, reported as direct holdings, and also discloses 80,000 shares held indirectly through an IRA. The filing includes a footnote that restricted shares vest at 20% per year beginning April 24, 2026.

Positive

• Director purchase activity: Darcey William acquired shares on 08/11/2025, indicating insider buying.
• Specified prices and amounts: Purchases documented as 4,861 shares at $17.30 and 139 shares at $17.29 provide clear transaction detail.
• Transparent ownership disclosure: Filing separates direct holdings and an indirect IRA holding of 80,000 shares and includes vesting terms for restricted stock.

Negative

• None.

Insights

Financial Analyst

TL;DR: Director purchases of NBBK stock were reported on 08/11/2025; sizes are modest versus large-cap norms and show continued insider ownership.

The filing documents two open-market purchases by Director Darcey William: 4,861 shares at $17.30 and 139 shares at $17.29. Reported beneficial ownership after those transactions is listed as 80,237 and 75,376 shares respectively, with an additional 80,000 shares held indirectly via an IRA. These are straightforward acquisitions with an attached restricted-stock vesting schedule that begins in April 2026.

Corporate Governance Expert

TL;DR: Routine Form 4 disclosure shows director buying shares and holding indirect IRA shares; restricted stock includes multi-year vesting.

The disclosure is consistent with standard Section 16 reporting: purchases coded as P, direct and indirect ownership identified, and a clear footnote describing restricted-stock vesting at 20% annually starting April 24, 2026. No departures, option exercises, or other governance issues are reported in this filing.

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).

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^*

Darcey William

(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)
08/11/2025

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	08/11/2025		P		139	A	$17.29	75,376(1)	D
Common Stock	08/11/2025		P		4,861	A	$17.3	80,237(1)	D
Common Stock								80,000	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	08/12/2025
	** 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 transactions did Darcey William report on Form 4 for NBBK?

The Form 4 reports purchases on 08/11/2025 of 4,861 shares at $17.30 and 139 shares at $17.29.

How many NBBK shares does Darcey William beneficially own after the reported transactions?

The filing lists beneficial ownership following the transactions as 80,237 shares and 75,376 shares on the respective reporting lines.

Does the Form 4 disclose any indirect holdings for Darcey William in NBBK?

Yes, the filing discloses 80,000 shares held indirectly

Are there any restrictions on shares reported by Darcey William?

Yes, a footnote states the reported shares include restricted stock that vests at 20% per year beginning April 24, 2026.

What transaction code is used for the reported purchases?

The purchases are coded with "P" in the filing, indicating purchase transactions.