NB Bancorp (NBBK) director corrects mistakenly reported share sale

Rhea-AI Filing Summary

NB Bancorp, Inc. director Kenneth C. Montgomery filed an amended Form 4 to update his holdings of common stock. The filing shows he beneficially owns 85,140 shares directly after correcting a previously reported change. A prior Form 4 filed on April 27, 2026 had mistakenly reported a disposition of common shares that did not actually occur, and this amendment reverses that error.

The holding includes restricted stock that vests 100% on January 2, 2027, as well as additional restricted shares that vest at a rate of 20% per year starting April 24, 2026. The amendment does not report any new purchase or sale, but clarifies his current equity position and the scheduled vesting of his awards.

Insider Trade Summary

1 transaction reported

Mixed 1 txn

Insider Montgomery Kenneth C.

Role null

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

Holdings After Transaction: Common Stock — 85,140 shares (Direct, null)

Footnotes (1)

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

Common shares owned: 85,140 shares Restricted stock full vest date: January 2, 2027 Annual vesting rate: 20% per year +1 more

4 metrics

Common shares owned 85,140 shares Direct beneficial ownership after correction

Restricted stock full vest date January 2, 2027 One grant vests 100% on this date

Annual vesting rate 20% per year Restricted stock vesting commencing April 24, 2026

Unknown transaction entries 1 entry Classified as holding with unknown code

Key Terms

restricted stock, beneficially owned, Form 4

3 terms

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.

beneficially owned financial

"The change in the securities beneficially owned has been corrected accordingly in this amended Form 4."

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.

Form 4 regulatory

"On April 27, 2026, a Form 4 was mistakenly filed reporting a disposition of shares of common stock that did not in fact occur."

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.

Form 4 Insider Transactions: What Each Field Means →

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)
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								85,140(1)(2)(3)	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.

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)

FAQ

What does Kenneth C. Montgomery’s amended Form 4 for NB Bancorp (NBBK) report?

The amended Form 4 updates Kenneth C. Montgomery’s direct holdings to 85,140 NB Bancorp common shares. It corrects a prior Form 4 that mistakenly showed a share disposition which, according to the filing, did not actually occur.

Did Kenneth C. Montgomery buy or sell NB Bancorp (NBBK) shares in this Form 4/A?

The Form 4/A does not report a new purchase or sale of NB Bancorp shares. Instead, it amends earlier disclosure by removing an erroneously reported disposition and restating his current beneficial ownership position.

How many NB Bancorp (NBBK) shares does Kenneth C. Montgomery now beneficially own?

After the correction, Kenneth C. Montgomery is reported as beneficially owning 85,140 shares of NB Bancorp common stock directly. This figure includes time-based restricted stock that will vest according to schedules described in the footnotes.

What restricted stock grants for NB Bancorp (NBBK) are disclosed in this Form 4/A?

The filing notes restricted stock that vests 100% on January 2, 2027. It also states that additional restricted shares vest at a rate of 20% per year, beginning on April 24, 2026, reflecting time-based equity compensation.

Why was the previous NB Bancorp (NBBK) Form 4 filing by Montgomery incorrect?

The footnotes explain that a Form 4 filed on April 27, 2026 mistakenly reported a disposition of NB Bancorp common stock. That disposition did not occur, and this amended Form 4 corrects the reported beneficial ownership.

Does the amended Form 4 for NB Bancorp (NBBK) change Montgomery’s derivative positions?

The insider data for this amended Form 4 shows no derivative securities transactions and an empty derivative position summary. The update focuses solely on correcting reported common stock ownership and restricted stock vesting details.