Rhinebeck Bancorp, Inc.

S-11 tm268293d1_s1.htm FORM S-1

As filed with the Securities and Exchange Commission on March 13, 2026

Registration No. 333-

UNITED STATES SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM S-1

REGISTRATION STATEMENT UNDER THE

SECURITIES ACT OF 1933

Rhinebeck Bancorp, Inc. and

Rhinebeck Bank 401(k) Plan

(Exact Name of Registrant as Specified in Its Charter)

2 Jefferson Plaza

**(845) 454-8555

**(Address, Including Zip Code, and Telephone Number, Including Area Code, of Registrant’s Principal Executive Offices)

Matthew J. Smith

President and Chief Executive Officer

Two Jefferson Plaza

**(845) 454-8555

**(Address, Including Zip Code, and Telephone Number, Including Area Code, of Agent for Service)

Copies to:

**Approximate date of commencement of proposed sale to the public:**As soon as practicable after this registration statement becomes effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box: x

If this Form is filed to register additional shares for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering:¨

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering:¨

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering:¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.:

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 to Section 7(a)(2)(B) of the Securities Act.¨

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

Prospectus Supplement

RHINEBECK BANK 401(k) PLAN

Offering of Participation Interests in up to 3,298,199 Shares of

Rhinebeck Bancorp, Inc. Common Stock

Rhinebeck Bancorp, Inc., a Maryland corporation that we refer to as “Rhinebeck Bancorp” throughout this prospectus supplement, is offering shares of common stock for sale at $10.00 per share in connection with the conversion of Rhinebeck Bancorp, MHC, a New York mutual holding company, from the mutual holding company structure to a fully public stock holding company structure. The shares being offered represent the ownership interest of Rhinebeck Bancorp, MHC in Rhinebeck Bancorp. Rhinebeck Bancorp’s common stock is currently traded on the Nasdaq Capital Market under the trading symbol “RBKB.” Upon the completion of the conversion and stock offering, we expect the shares of Rhinebeck Bancorp common stock will continue to trade on the Nasdaq Capital Market under the symbol “RBKB.”

In connection with the offering, Rhinebeck Bank, the wholly owned subsidiary of Rhinebeck Bancorp, is allowing participants in the Rhinebeck Bank 401(k) Plan, as adopted by Rhinebeck Bank (the “401(k) Plan”), to invest a portion of their account balances in Rhinebeck Bancorp common stock. This prospectus supplement relates to the elections by 401(k) Plan participants to direct the trustee of the 401(k) Plan to invest all or a portion of their account balances in the 401(k) Plan in Rhinebeck Bancorp common stock at the time of the offering. Based upon the value of the 401(k) Plan assets as of December 31, 2025, the trustee of the 401(k) Plan could purchase up to 3,298,199 shares of Rhinebeck Bancorp common stock at the purchase price of $10.00 per share.

Before you consider investing, you should read the prospectus of Rhinebeck Bancorp, dated ___________, which accompanies this prospectus supplement. It contains detailed information regarding the stock offering of Rhinebeck Bancorp common stock and the financial condition, results of operations and business of Rhinebeck Bank. This prospectus supplement provides information regarding the 401(k) Plan. You should read this prospectus supplement together with the prospectus and keep both for future reference.

For a discussion of risks that you should consider, see “Risk Factors” beginning on page 17 of the accompanying prospectus and “Notice of Your Rights Concerning Employer Securities” in this prospectus supplement.

The interests in the 401(k) Plan and the offering of the shares of Rhinebeck Bancorp common stock have not been approved or disapproved by the Board of Governors of the Federal Reserve System, the New York State Department of Financial Services, the Securities and Exchange Commission, the Federal Deposit Insurance Corporation nor any other federal or state securities regulator. Any representation to the contrary is a criminal offense.

The securities offered in this prospectus supplement are not deposits or accounts and are not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

This prospectus supplement may be used only in connection with offers and sales by Rhinebeck Bancorp of participation interests in shares of Rhinebeck Bancorp common stock pursuant to the 401(k) Plan. No one may use this prospectus supplement to re-offer or resell participation interests or shares of Rhinebeck Bancorp common stock acquired through the 401(k) Plan.

You should rely only on the information contained in this prospectus supplement and the accompanying prospectus. Rhinebeck Bancorp, Rhinebeck Bank and the 401(k) Plan have not authorized anyone to provide you with information that is different.

This prospectus supplement does not constitute an offer to sell or solicitation of an offer to buy any securities in any jurisdiction to any person to whom it is unlawful to make an offer or solicitation in that jurisdiction. Neither the delivery of this prospectus supplement and the prospectus nor any sale of Rhinebeck Bancorp common stock or participation interests representing an ownership interest in Rhinebeck Bancorp common stock shall under any circumstances imply that there has been no change in the affairs of Rhinebeck Bancorp, Rhinebeck Bank or the 401(k) Plan since the date of this prospectus supplement, or that the information contained in this prospectus supplement or incorporated by reference is correct as of any time after the date of this prospectus supplement.

The date of this prospectus supplement is ___________.