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8-K

NB Bancorp, Inc. (NBBK)

8-K 2025-10-08 For: 2025-10-07
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UNITED STATES

SECURITIES AND EXCHANGECOMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of Earliest

Event Reported): October 7, 2025

NB

BANCORP, INC.

(Exact Name of Registrant as Specified in Charter)

Maryland 001-41899 93-2560883
(State<br> or Other Jurisdiction (Commission (I.R.S.<br> Employer
of<br> Incorporation or Organization) File<br> Number) Identification<br> Number)
1063<br> Great Plain Avenue
--- ---
Needham,<br> Massachusetts 02492
(Address<br> of Principal Executive Offices) (Zip<br> Code)

Registrant’s telephone

number, including area code: (781) 444-2100

Not Applicable

(Former name or formeraddress, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the Registrant under any of the following provisions:

¨ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
¨ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
--- ---
¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
--- ---
¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))
--- ---

Securities registered pursuant to Section 12(b) of the Act:

Title<br> of each class Trading<br><br><br> Symbol(s) Name<br> of each exchange on<br><br> which registered
Common<br> Stock NBBK The<br> Nasdaq Stock Market, LLC

Indicate by check mark whether the Registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company x

If an emerging growth company, indicate by check mark if the Registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Item 8.01 Other Events.

NB Bancorp, Inc. (“Needham”), the holding company for Needham Bank, and Provident Bancorp, Inc. (“Provident”), the holding company for BankProv, today announced that the election form and letter of transmittal (together with the related instructions, the “Election Materials”) have been distributed to holders of Provident common stock, so Provident stockholders may elect to receive either Needham common stock, cash or a combination of both upon the completion of the pending combination of Needham and Provident. A copy of the press release is attached to this Current Report on Form 8-K as Exhibit 99.1 and is incorporated herein by reference.

As previously disclosed, on June 5, 2025, Needham, Needham Bank, Provident and BankProv entered into an Agreement and Plan of Merger (the “Merger Agreement”) pursuant to which Needham will acquire Provident and BankProv through the merger of 1828 MS, Inc. (a Maryland corporation and wholly owned subsidiary of Needham formed to facilitate the merger) with and into Provident, with Provident as the surviving corporation (the “Parent Merger”). Next, Provident will merge with and into Needham, with Needham as the surviving entity (the “Holdco Merger”), and, immediately thereafter, BankProv will merge with and into Needham Bank, with Needham Bank as the surviving entity (the “Bank Merger” and, together with the Parent Merger and the Holdco Merger, the “Merger Transaction”).

On September 16, 2025, Provident announced that its stockholders approved the Merger Agreement.

Needham anticipates that all required regulatory approvals will be received and all of the other closing conditions will be satisfied by November 14, 2025, and the Merger Transaction will become effective on November 15, 2025, although Needham cannot provide any assurance that all required regulatory approvals, waivers or consents will be obtained, when they will be obtained, or whether there will be burdensome conditions in the approvals or any litigation challenging the approvals.

Mailingof Election Materials

On October 7, 2025, Continental Stock Transfer & Trust Company, the exchange agent appointed by Needham (the “Exchange Agent”), mailed the Election Materials to holders of record of Provident common stock to make an election (the “Election”) as to the form of merger consideration they wish to receive in exchange for the Provident common stock they own. The Election process for Provident stockholders is referred to herein as the “Stockholder Election Process.” A copy of the Election Materials is attached to this Current Report on Form 8-K as Exhibit 99.2 and is incorporated herein by reference.

As further described in the Election Materials, for a Provident stockholder to make a valid election, a properly completed Election Form and any Provident stock certificate(s), together with any other required documents described in the Election Materials, must be received by the Exchange Agent prior to the election deadline, which is anticipated to be 5:00 p.m. (Eastern Time) on November 7, 2025 (with an earlier deadline of 5:00 p.m. (Eastern Time) on October 31, 2025 for those who own Provident common stock through the Provident ESOP and 401(k) plans). Needham and Provident intend to announce the definitive election deadline (the “Election Deadline”) at least five business days (but not more than 15 business days) prior to the Election Deadline.

Needham has engaged Alliance Advisors, LLC, to serve as information agent (the “Information Agent”) in connection with the Stockholder Election Process. Provident stockholders who have questions about the Stockholder Election Process, want up-to-date information on the Election Deadline or wish to obtain copies of the Election Materials may contact Alliance Advisors, LLC 150 Clove Road, Suite 400, Little Falls, NJ 07424, via telephone at (855) 206-1249, or via email at NBBK@allianceadvisors.com.

Provident stockholders may also contact their broker, dealer, commercial bank or trust company or other nominee, if applicable, for assistance concerning the Merger Transaction and the Stockholder Election Process.

Elections made by Provident stockholders are subject to the allocation and proration provisions in the Merger Agreement, which are summarized in the Election Materials and the proxy statement/prospectus, which forms part of the registration statement on Form S-4 (File No. 333-288494) that Needham filed with the Securities and Exchange Commission on July 30, 2025. (In the event of any inconsistency between the Merger Agreement and the Election Materials or the definitive proxy statement/prospectus, the terms of the Merger Agreement will control.)

Provident stockholders and participants in Provident’s ESOP and 401(k) plan should carefully read the Election Materials provided to them, as well as the relevant portions of the definitive proxy statement/prospectus and the Merger Agreement, before making their elections.

Caution Regarding Forward-Looking Statements

This Current Report on Form 8-K contains “forward-looking statements” within the meaning of section 27A of the Securities Act of 1933, as amended, and section 21E of the Securities Exchange Act of 1934, as amended. Forward-looking statements include statements regarding anticipated future events and can be identified by the fact that they do not relate strictly to historical or current facts. You can identify these statements from the use of the words “may,” “will,” “should,” “could,” “would,” “plan,” “potential,” “estimate,” “project,” “believe,” “intend,” “anticipate,” “expect,” “target” and similar expressions. Forward-looking statements, by their nature, are subject to risks and uncertainties. There are many factors that could cause actual results to differ materially from expected results described in the forward-looking statements.

Factors relating to the proposed Merger Transaction that could cause or contribute to actual results differing materially from expected results include, but are not limited to, the possibility that revenue or expense synergies or the other expected benefits of the Merger Transaction may not materialize in the timeframe expected or at all, or may be more costly to achieve; that the Merger Transaction may not be timely completed, if at all; that prior to the completion of the Merger Transaction or thereafter, Needham or Provident may not perform as expected due to Merger Transaction-related uncertainty or other factors; that Needham is unable to successfully implement its integration strategies; that required regulatory or other approvals are not obtained or other closing conditions are not satisfied in a timely manner or at all; that the Merger Agreement closing conditions are not satisfied in a timely manner or at all; that the timing of completion of the proposed Merger Transaction is dependent on various factors that cannot be predicted with precision at this point; reputational risks and the reaction of the companies’ customers to the Merger Transaction; the inability to implement onboarding or transition plans and other consequences associated with the Merger Transaction; continued pressures and uncertainties within the banking industry and Needham’s and Provident’s markets, including changes in interest rates and deposit amounts and composition, adverse developments in the level and direction of loan delinquencies, charge-offs, and estimates of the adequacy of the allowance for credit losses, increased competitive pressures, asset and credit quality deterioration, and legislative, regulatory, and fiscal policy changes and related compliance costs; and diversion of management time on Merger Transaction-related issues.

These forward-looking statements are also subject to the risks and uncertainties applicable to the businesses of Needham and Provident generally that are disclosed in Needham’s and Provident’s respective 2024 Annual Reports on Form 10-K. Needham’s and Provident’s SEC filings are accessible on the SEC's website at sec.gov and on their respective corporate websites of Needham and Provident at nbbancorp.com and investors.bankprov.com. These web addresses are included as inactive textual references only. Information on these websites is not part of this document. For any forward-looking statements made in this press release, Needham and Provident claim the protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995. Except as required by law, each company specifically disclaims any obligation to update any forward-looking statements as a result of developments occurring after the date of this press release.

Item 9.01 Financial Statements and Exhibits.

(d)       Exhibits.

ExhibitNumber Description
99.1 Press Release dated October 8,<br>2025
99.2 Election Materials
104 Cover Page Interactive Data File<br>(embedded within Inline XBRL documents)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the Registrant has duly caused this report to be signed on its behalf by the undersigned, hereunto duly authorized.

NB<br> BANCORP, INC.
By: /s/<br> Jean-Pierre Lapointe
DATE: October 8, 2025 Executive Vice President and Chief Financial Officer

Exhibit 99.1

NB Bancorp, Inc. and Provident Bancorp, Inc.

Announce Mailing of Stock/Cash Election Form


NEEDHAM,Mass & AMESBURY, Mass, October 8, 2025 – NB Bancorp, Inc. (“Needham”) (Nasdaq: NBBK), the holding company for Needham Bank, and Provident Bancorp, Inc. (“Provident”) (Nasdaq: PVBC), the holding company for BankProv, today announced that the election form and letter of transmittal (together with the related instructions, the “Election Materials”) have been distributed to holders of Provident common stock so Provident stockholders may elect to receive either Needham common stock, cash or a combination of both upon the completion of the pending combination of Needham and Provident.

On June 5, 2025, Needham, Needham Bank, Provident, and BankProv entered into an Agreement and Plan of Merger (the “Merger Agreement”) pursuant to which Provident will merge with and into Needham, with Needham as the surviving entity (the “Holdco Merger”), and, immediately thereafter, BankProv will merge with and into Needham Bank, with Needham Bank as the surviving entity (the “Bank Merger” and, together with the Holdco Merger, the “Merger Transaction”).

On September 16, 2025, Provident announced that its stockholders had approved the Merger Agreement.

Needham anticipates that all required regulatory approvals will be received and all of the other closing conditions will be satisfied by November 14, 2025, and the Merger Transaction will become effective on November 15, 2025, although Needham cannot provide any assurance that all required regulatory approvals, waivers or consents will be obtained, when they will be obtained, or whether there will be burdensome conditions in the approvals or any litigation challenging the approvals.

Stock and Cash Merger Consideration

As disclosed previously, including in the definitive proxy statement/prospectus filed by Needham with the Securities and Exchange Commission (the “SEC”) on July 30, 2025 (the “proxy statement/prospectus”), at the effective time of the Holdco Merger (the “Effective Time”), shares of Provident common stock issued and outstanding immediately prior to the Effective Time will be converted into the right to receive, at the election of each Provident stockholder, and subject to the allocation, proration and other procedures specified in the Merger Agreement, either:

· 0.691<br> shares of Needham common stock per share of Provident common stock (“Stock Consideration”);<br> or
· $13.00<br> in cash per share of Provident common stock (“Cash Consideration”).
--- ---

Provident stockholders may also elect to receive a combination of Stock Consideration and Cash Consideration, subject to the allocation, proration and other procedures specified in the Merger Agreement.

1

The Stock Consideration and Cash Consideration are collectively referred to as the “Merger Consideration.” The receipt of the Merger Consideration will be subject in each case to applicable withholding taxes, if any, and be payable without interest.

The allocation and proration provisions in the Merger Agreement ensure that 50% of the shares of Provident common stock will receive the Stock Consideration and 50% of the shares of Provident common stock will receive the Cash Consideration. (The allocation and proration procedures specified in the Merger Agreement are summarized in the Election Materials and the definitive proxy statement/prospectus.)

Stockholder Election Process

As further described in the Election Materials, for a Provident stockholder to make a valid election, a properly completed Election Form and any Provident stock certificate(s), together with any other required documents described in the Election Materials, must be received by the Exchange Agent prior to the election deadline, which is anticipated to be 5:00 p.m. (Eastern Time) on November 7, 2025. Needham and Provident intend to announce the definitive election deadline (the “Election Deadline”) at least five business days (but not more than 15 business days) prior to the Election Deadline. Provident stockholders who hold their shares through a broker, bank, trustee or other nominee should follow the instructions of such broker, bank, trustee or other nominee as to the procedures for making elections and exchanging their shares of Provident common stock. For shares with respect to which a Provident stockholder has made an election as of the Election Deadline, those shares may not be traded through the Effective Time. Provident Employee Stock Ownership Plan (“ESOP”) and 401(k) plan participants must make their Elections with respect to their indirect beneficial ownership of Provident common stock through the ESOP and 401(k) plans no later than 5:00 p.m. (Eastern Time) on October 31, 2025. Provident stockholders and plan participants should carefully read the Election Materials provided to them, as well as the relevant portions of the proxy statement/prospectus and the Merger Agreement, before making their elections.

Any Provident stockholder who does not make a proper election by the Election Deadline will have their shares of Provident common stock exchanged for Stock Consideration, Cash Consideration or a combination of the two depending on the valid elections of other Provident stockholders and subject to the allocation and proration procedures in the Merger Agreement. Provident ESOP and 401(k) plan participants who do not make a proper and timely election with respect to their indirect beneficial ownership of Provident common stock through the ESOP and/or 401(k) plans will have their shares elected by the respective plan trustee in proportion to the elections made by other plan participants, subject to the allocation and proration procedures in the Merger Agreement. A Provident stockholder of shares purchased after the Election Deadline will not be permitted to submit an election with respect to those shares.

Provident stockholders who have questions about the Stockholder Election Process, want up-to-date information on the Election Deadline or wish to obtain copies of the Election Materials may contact Alliance Advisors, LLC, Needham’s information agent for the Stockholder Election Process, 150 Clove Road, Suite 400, Little Falls, NJ 07424, via telephone at (855) 206-1249, or via email at NBBK@allianceadvisors.com.

Additional Information and Where to Find It

Electronic copies of the Merger Agreement, the definitive proxy statement/prospectus and the Election Materials, as well as other filings containing information about Needham and Provident, may be obtained at the website of the SEC at sec.gov; and on the respective corporate websites of Needham and Provident at nbbancorp.com and investors.bankprov.com. (These web addresses are included as inactive textual references only.) Copies of the Merger

Agreement, the proxy statement/prospectus and the Election Materials are also available, without charge, through Needham’s Investor Relations via email at ir@needhambank.com or by telephone at (781) 474-5408, or to Provident Investor Relations via email at kfisher@bankprov.com or by telephone at (603) 318-2660.

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Forward Looking Statements

This press release contains “forward-looking statements” within the meaning of section 27A of the Securities Act of 1933, as amended, and section 21E of the Securities Exchange Act of 1934, as amended. Forward-looking statements include statements regarding anticipated future events and can be identified by the fact that they do not relate strictly to historical or current facts. You can identify these statements from the use of the words “may,” “will,” “should,” “could,” “would,” “plan,” “potential,” “estimate,” “project,” “believe,” “intend,” “anticipate,” “expect,” “target” and similar expressions. Forward-looking statements, by their nature, are subject to risks and uncertainties. There are many factors that could cause actual results to differ materially from expected results described in the forward-looking statements.

Factors relating to the proposed Merger Transaction that could cause or contribute to actual results differing materially from expected results include, but are not limited to, the possibility that revenue or expense synergies or the other expected benefits of the Merger Transaction may not materialize in the timeframe expected or at all, or may be more costly to achieve; that the Merger Transaction may not be timely completed, if at all; that prior to the completion of the Merger Transaction or thereafter, Needham or Provident may not perform as expected due to Merger Transaction-related uncertainty or other factors; that Needham is unable to successfully implement its integration strategies; that required regulatory or other approvals are not obtained or other closing conditions are not satisfied in a timely manner or at all; that the timing of completion of the proposed Merger Transaction is dependent on various factors that cannot be predicted with precision at this point; reputational risks and the reaction of the companies’ customers to the Merger Transaction; the inability to implement onboarding or transition plans and other consequences associated with the Merger Transaction; continued pressures and uncertainties within the banking industry and Needham and Provident’s markets, including changes in interest rates and deposit amounts and composition, adverse developments in the level and direction of loan delinquencies, charge-offs, and estimates of the adequacy of the allowance for credit losses, increased competitive pressures, asset and credit quality deterioration, and legislative, regulatory, and fiscal policy changes and related compliance costs; and diversion of management time on Merger Transaction-related issues.

These forward-looking statements are also subject to the risks and uncertainties applicable to our the businesses of Needham and Provident generally that are disclosed in Needham’s and Provident’s respective 2024 Annual Reports on Form 10-K. Needham’s and Provident’s SEC filings are accessible on the SEC's website at sec.gov and on their respective corporate websites of Needham and Provident at nbbancorp.com and investors.bankprov.com. These web addresses are included as inactive textual references only. Information on these websites is not part of this press release. For any forward-looking statements made in this press release, Needham and Provident claim the protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995. Except as required by law, each company specifically disclaims any obligation to update any forward-looking statements as a result of developments occurring after the date of this press release.

ABOUT NB BANCORP, INC.

NB Bancorp, Inc. (Nasdaq Capital Market: NBBK) is the registered bank holding company of Needham Bank. Needham Bank is

headquartered in Needham, Massachusetts, which is approximately 17 miles southwest of Boston's financial district. Known as the “Builder's Bank,” Needham Bank has been helping individuals, businesses and non-profits build for their futures since 1892. Needham Bank offers an array of tech-forward products and services that businesses and consumers use to manage their financial needs. For more information, please visit https://NeedhamBank.com.

ABOUT PROVIDENT BANCORP, INC.

Provident Bancorp, Inc. (Nasdaq: PVBC) is the holding company for BankProv, a full-service commercial bank headquartered in Massachusetts. With retail branches in the North Shore of Massachusetts and in southern New Hampshire, commercial banking offices in the Manchester/Concord market in Central New Hampshire and a loan office located in Ponte Vedra Beach, Florida, BankProv delivers a unique combination of traditional banking services and innovative financial solutions to its markets. For more information, visit www.bankprov.com.

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3

Exhibit99.2

STOCK/CASHELECTION FORM AND LETTER OF TRANSMITTAL

PURSUANTTO THE AGREEMENT AND PLAN OF MERGER, DATED AS OF JUNE 5, 2025 (“MERGER AGREEMENT”), BY AND AMONG NB BANCORP, INC., 1828 MS,INC., NEEDHAM BANK, PROVIDENT BANCORP, INC., AND BANKPROV, PURSUANT TO WHICH PROVIDENT BANCORP, INC. WILL MERGE WITH AND INTO NB BANCORP,INC. (THE “MERGER”).

Certificate
Name(s)<br> and Addresses of Registered Holder(s)<br><br>(If<br> there is any error in the name or address shown below, please make the necessary<br> corrections) Number(s)/Security<br><br> Listing<br> Number(s) Number<br><br> of<br> Shares
(If<br> additional space is needed, attach a signed schedule to this document) TOTAL<br> SHARES

THEINSTRUCTIONS ACCOMPANYING THIS STOCK/CASH ELECTION FORM AND LETTER OF TRANSMITTAL SHOULD BE READ CAREFULLY BEFORE THIS STOCK/CASH ELECTIONFORM AND LETTER OF TRANSMITTAL IS COMPLETED.

FAILURETO COMPLETE THE SUBSTITUTE FORM W-9 INCLUDED IN THIS STOCK/CASH ELECTION FORM AND LETTER OF TRANSMITTAL MAY SUBJECT YOU TO BACKUP WITHHOLDING.

PLEASECOMPLETE, SIGN AND MAIL OR DELIVER THIS STOCK/CASH ELECTION FORM AND LETTER OF TRANSMITTAL, TOGETHER WITH THE CERTIFICATE(S) REPRESENTINGYOUR SHARES OF PROVIDENT BANCORP, INC. COMMON STOCK, IN THE ENCLOSED ENVELOPE TO THE EXCHANGE AGENT:

CONTINENTALSTOCK TRANSFER & TRUST COMPANY

ByHand or Overnight Delivery:

Continental Stock Transfer & Trust Company

1 State Street – 30th Floor

New York, New York 10004

ElectronicUpload (Non-Transfer/Book Entry ONLY):

https://cstt.sharefile.com/r-rbe89ba15f1ed45b0b8ff15e7766f98b3

Ifyou have questions or need assistance, please contact Alliance Advisors, LLC, 150 Clove Road, Suite 400, Little Falls, NJ 07424, Toll-freeat 1-855-206-1249, or NBBK@allianceadvisors.com.

THEELECTION DEADLINE IS 5:00 P.M., EASTERN TIME, ON NOVEMBER 7, 2025. THIS STOCK/CASH ELECTION FORM AND LETTER OF TRANSMITTAL MUST BE COMPLETED,SIGNED AND RECEIVED BY THE EXCHANGE AGENT, ALONG WITH YOUR STOCK CERTIFICATE(S), IF APPLICABLE, NO LATER THAN THIS TIME.

Subjectto the conditions and limitations set forth in the Merger Agreement, the undersigned hereby elects to receive the following as considerationfor the undersigned’s shares of Provident Bancorp, Inc., common stock. Any capitalized term not defined in this Stock/Cash ElectionForm and Letter of Transmittal shall have the meaning set forth in the Merger Agreement.

(Pleasecheck one box only to indicate your election.)

(1) Stock Election – All shares of Provident Bancorp, Inc. common stock I own converted into<br> the Stock Election Consideration.
(2) Cash Election – All shares of Provident Bancorp, Inc. common stock I own converted into<br> the Cash Election Consideration.
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(3) Mixed Election – A combination of stock and cash as follows:
--- ---

__________shares of Provident Bancorp, Inc. common stock converted into the Stock Election Consideration; and

__________shares of Provident Bancorp, Inc. common stock converted into the Cash Election Consideration.

__________Total (cannot exceed the total number of Provident Bancorp, Inc. shares you own of record)

(4) Non-Election<br> – Your Provident Bancorp, Inc. shares will be deemed “Non-Election Shares”<br> if:
· You<br> check this box, thereby indicating that you have no preference as to the form of Merger Consideration that you will receive;
--- ---
· No<br> choice is indicated above under (1), (2) or (3);
--- ---
· More<br> than one choice is indicated above under (1), (2) and (3);
--- ---
· You<br> fail to follow the instructions on this Stock/Cash Election Form and Letter of Transmittal or otherwise fail properly to make an election;<br> or
--- ---
· A<br> completed Stock/Cash Election Form and Letter of Transmittal (including submission of your Provident Bancorp, Inc. common stock certificate(s))<br> is not actually received by the Exchange Agent (as defined below) by the Election Deadline.
--- ---

Ifyour Provident Bancorp, Inc. shares are deemed Non-Election Shares, you will receive the Stock Election Consideration and/or the CashElection Consideration as determined pursuant to the proration provisions of the Merger Agreement without regard to your preferences.

The undersigned represents that the undersigned has full authority to surrender without restriction the certificate(s) representing shares of Provident Bancorp, Inc. common stock for exchange. Please evidence the shares of NB Bancorp, Inc. common stock in book entry form and/or the check for cash in lieu of a fractional share interest or the Cash Election Consideration in the name shown above to the above address unless instructions are given under “Special Issuance/Payment Instructions” and/or “Special Delivery Instructions” below.

YOU MUST SIGN BELOW
* SIGNATURE(S) REQUIRED * SIGNATURE(S)<br> GUARANTEED (IF REQUIRED)
Signature(s)<br> of Registered Holder(s) or Agent (SEE INSTRUCTION 12.)
Must<br> be signed by the registered holder(s) EXACTLY as<br> name(s) appears on stock certificate(s)/security listing(s).<br> If signature is by a trustee, executor, administrator,<br> guardian, attorney-in-fact, officer for a corporation<br> acting in a fiduciary or representative capacity,<br> or other person, please set forth full title. (SEE INSTRUCTIONS<br> 11 AND 12.) Unless<br> the shares are tendered by the registered holder(s) of the<br> common stock, or for the account of a member of a<br> Signature Guarantee Program, Stock Exchange Medallion<br> Program or New York Stock Exchange Medallion<br> Signature Program, your signature(s) must be guaranteed by<br> an Eligible Institution. (SEE INSTRUCTION<br> 12.)
Registered<br> Holder Authorized<br> Signature
Registered<br> Holder Name<br> of Firm
Telephone<br> number
Email<br> address Address<br> of Firm (Please Print)
Title,<br> if any
Date: Date:
SPECIAL ISSUANCE/PAYMENT INSTRUCTIONS SPECIAL DELIVERY INSTRUCTIONS
Complete<br> ONLY if the evidence of shares of NB Bancorp,<br> Inc. common stock in book entry form and/or check<br> is to be issued in a name that differs from the name on<br> the surrendered certificate(s). Complete<br> ONLY if the evidence of shares of NB Bancorp,<br> Inc. common stock in book entry form and/or check<br> is to be sent to an address other than the address reflected<br> above.
Issue<br> to:
Mail<br> to:
Name
Address Name
Address
(Please<br>also complete Substitute Form W-9 on page 6 AND<br>see instructions regarding signature guarantee. SEE INSTRUCTIONS 12, 13 and 14.) (SEE INSTRUCTION 13.)

PLEASEALSO SIGN AND PROVIDE YOUR TAX ID NUMBER IN SUBSTITUTE TAX FORM

ASA RESULT OF COMPLETING AND SIGNING THIS STOCK/CASH ELECTION FORM AND LETTER OF TRANSMITTAL IN ACCORDANCE WITH THE INSTRUCTIONS, YOU WILLNOT NEED TO SIGN THE BACK OF YOUR PROVIDENT BANCORP, INC. STOCK CERTIFICATE(S) IF APPLICABLE.

INSTRUCTIONS

(Please read carefully the instructions below)

Ifyou have any questions, please contact Alliance Advisors, LLC, 150 Clove Road, Suite 400, Little Falls, NJ 07424, Toll-free at 1-855-206-1249,or NBBK@allianceadvisors.com.

1.             ELECTION DEADLINE: For any election contained herein to be considered, this Stock/Cash Election Form and Letter of Transmittal, properlycompleted and signed, together with the related Provident Bancorp, Inc. common stock certificate(s), MUST BE RECEIVED BY THE EXCHANGEAGENT AT THE ADDRESS ON THE FRONT OF THIS STOCK/CASH ELECTION FORM AND LETTER OF TRANSMITTAL NO LATER THAN 5:00 P.M., EASTERN TIME, ONNOVEMBER 7, 2025. NB Bancorp, Inc. has the discretion, which it may delegate to Continental Stock Transfer & Trust Company (the “Exchange Agent”), to determine whether any Stock/Cash Election Form and Letter of Transmittal is received on a timely basis and whether a Stock/Cash Election Form and Letter of Transmittal has been properly completed.

2.             DESCRIPTION OF SHARES: Insert in the box at the top of this Stock/Cash Election Form and Letter of Transmittal the certificate number(s)/security listing number(s) of each certificate evidencing Provident Bancorp, Inc. common stock that you are surrendering herewith, the number of shares represented by each certificate, if any, and the name(s) and address(es) of the registered owners of such shares. If the space provided is insufficient, attach a separate sheet listing this information.

3 ELECTION OPTIONS: On page 2 of this Stock/Cash Election Form and Letter of Transmittal, you may indicate whether you would like to receive, in exchange for your shares of Provident Bancorp, Inc. common stock, the Stock Election Consideration, the Cash Election Consideration or a combination of the Stock Election Consideration and the Cash Election Consideration. Alternatively, you may indicate that you have no preference as to the form of Merger Consideration that you will receive. Mark only one selection. The Merger Agreement provides that 50% of the shares of Provident Bancorp, Inc. common stock outstanding immediately prior to the effective time of the Merger will be exchanged for the Stock Election Consideration, with the remaining 50% of the shares of Provident Bancorp, Inc. common stock outstanding as of the Merger exchanged for the Cash Election Consideration. Therefore, you might receive NB Bancorp, Inc. common stock and/or cash in an amount that is not consistent with your election, depending upon the elections of other Provident Bancorp, Inc. shareholders. Provident Bancorp, Inc. shareholders who are deemed to have made a non-election may receive all cash, all stock or a mix of cash/stock consideration, depending upon the elections of other Provident Bancorp, Inc. shareholders.

4.             NOMINEES: Any record holder of shares of Provident Bancorp, Inc. common stock who is a nominee may submit one or more Stock/Cash Election Forms and Letters of Transmittal indicating on the form or forms a combination of elections covering up to the aggregate number of shares of Provident Bancorp, Inc. common stock owned by such record holder. However, upon the request of NB Bancorp, Inc., such record holders will be required to certify to the satisfaction of NB Bancorp, Inc. that such record holder holds such shares of Provident Bancorp, Inc. common stock as nominee for the beneficial owners of such shares.

5.             REVOCATION OR CHANGE OF STOCK/CASH ELECTION FORM AND LETTER OF TRANSMITTAL: Any Stock/Cash Election Form and Letter of Transmittal may be revoked or changed by written notice from the person submitting such form to the Exchange Agent for the Merger, but to be effective, such notice must be received by the Exchange Agent at or prior to the Election Deadline. NB Bancorp, Inc. will have the discretion, which it may delegate to the Exchange Agent, to determine whether any revocation or change is received on a timely basis and whether any such revocation or change has been properly made.

6.             SURRENDER OF CERTIFICATE(S): For any election contained herein to be effective, this Stock/Cash Election Form and Letter of Transmittal must be accompanied by any certificate(s) evidencing your shares and any required accompanying evidence of authority (see Instruction 11).

7.             LOST CERTIFICATE(S): If the certificate(s) that a registered holder (or transferee) wants to surrender has (have) been lost or destroyed, that holder should promptly contact the transfer agent for Provident Bancorp, Inc. common stock, Continental Stock Transfer & Trust Company, to arrange for the replacement of the lost or destroyed certificate(s) with new certificates to be delivered to the Exchange Agent with this Stock/Cash Election Form and Letter of Transmittal, properly completed and duly executed, prior to the Election Deadline.

8.             TERMINATION OF MERGER: In the event of termination of the Merger Agreement, the Exchange Agent will promptly return certificates representing shares of Provident Bancorp, Inc. common stock after being notified of such termination by NB Bancorp, Inc. or Provident Bancorp, Inc. In such event, shares of Provident Bancorp, Inc. common stock held through nominees are expected to be available for sale or transfer promptly following the termination of the Merger Agreement. Certificates representing shares of Provident Bancorp, Inc. common stock held directly by Provident Bancorp, Inc. shareholders will be returned by registered mail.

9.              METHOD OF DELIVERY: Your Provident Bancorp, Inc. stock certificate(s) and this Stock/Cash Election Form and Letter of Transmittal must be delivered to the Exchange Agent. Do not send them to NB Bancorp, Inc. or Provident Bancorp, Inc. The method of delivery of certificates and other documents to be delivered to the Exchange Agent at the address set forth on the front of this Stock/Cash Election Form and Letter of Transmittal is at the option and risk of the surrendering shareholder. Delivery will be deemed effected, and risk of loss and title to certificates shall pass, only upon proper delivery of such certificates to the Exchange Agent. If the certificate(s) are sent by mail, registered mail with return receipt requested and properly insured is recommended. A return envelope is enclosed.

10.           EVIDENCE OF SHARES/CHECK ISSUED IN THE SAME NAME: If the shares in book entry form representing NB Bancorp, Inc. common stock are to be evidenced and/or the check is to be issued in the same name as the surrendered certificate is registered, this Stock/Cash Election Form and Letter of Transmittal should be completed and signed exactly as the surrendered certificate is registered. Signature guarantees are not required if the certificate(s) surrendered herewith are submitted by the registered owner of such shares who has not completed the section entitled “Special Issuance/Payment Instructions” or are for the account of an Eligible Institution, as defined below. If any of the shares surrendered hereby are owned by two or more joint owners, all such owners must sign this Stock/Cash Election Form and Letter of Transmittal exactly as written on the face of the certificate(s). If any shares are registered in different names on several certificates, it will be necessary to complete, sign and submit as many separate Stock/Cash Election Forms and Letters of Transmittal as there are different registrations. Stock/Cash Election Forms and Letters of Transmittal executed by trustees, executors, administrators, guardians, officers of corporations, or others acting in a fiduciary capacity who are not identified as such in the registration must be accompanied by proper evidence of the signer’s authority to act.

11.           EVIDENCE OF SHARES/CHECK ISSUED IN DIFFERENT NAME: If the section entitled “Special Issuance/Payment Instructions” is completed, then signatures on this Stock/Cash Election Form and Letter of Transmittal must be guaranteed by a firm that is a bank, broker, dealer, credit union, savings association or other entity which is a member in good standing of the Securities Transfer Agents Medallion Program (each an “Eligible Institution”).

12.           SPECIAL ISSUANCE/PAYMENT AND DELIVERY INSTRUCTIONS: Indicate the name and address in which the shares in book entry form representing NB Bancorp, Inc. common stock are to be evidenced and/or check is to be sent if different from the name and/or address of the person(s) signing this Stock/Cash Election Form and Letter of Transmittal. The shareholder is required to give the social security number or employer identification number of the record owner of the shares. If Special Issuance/Payment Instructions have been completed, the shareholder named therein will be considered the record owner for this purpose.

13.           STOCK TRANSFER TAXES: If any shares of NB Bancorp, Inc. common stock are to be evidenced in book entry form or any payment of the cash consideration or cash in lieu of fractional shares is to be made in a name other than that of the registered holder(s) of the surrendered Provident Bancorp, Inc. certificate(s), it shall be a condition of such issuance and/or payment that the person requesting such exchange either (i) pay to the Exchange Agent in advance any transfer or other taxes required by reason of the issuance or payment to a person other than the registered holder(s), or (ii) establish to the satisfaction of the Exchange Agent that such tax has been paid or is not applicable.

14.           CONSTRUCTION: All questions with respect to this Stock/Cash Election Form and Letter of Transmittal raised by holders of Provident Bancorp, Inc. common stock (including, without limitation, questions relating to the time limits or effectiveness of revocation of any election and questions relating to computations as to allocations) will be determined by NB Bancorp, Inc. and/or the Exchange Agent, whose determination shall be conclusive and binding. NB Bancorp, Inc. shall have the right to reject any and all Stock/Cash Election Forms and Letters of Transmittal not in the proper form or to waive any irregularities in any such form, although it does not represent that it will do so. NB Bancorp, Inc. and/or the Exchange Agent may, but are not required to, take reasonable action to inform holders of Provident Bancorp, Inc. common stock of any defects and may take reasonable action to assist such holders to correct any such defects; however, neither NB Bancorp, Inc. nor the Exchange Agent is under any obligation to notify a holder of shares of Provident Bancorp, Inc. common stock of any defect in a Stock/Cash Election Form and Letter of Transmittal.

15.         QUESTIONS: If you have any questions or would like to receive additional or multiplecopies of this Stock/Cash Election Form and Letter of Transmittal, please contact Alliance Advisors, LLC, 150 Clove Road, Suite 400,Little Falls, NJ 07424, Toll-free at 1-855-206-1249, or NBBK@allianceadvisors.com.