UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER
PURSUANT TO RULE 13a-16 OR 15d-16
UNDER THE SECURITIES EXCHANGE ACT OF 1934

Date of Report: January 21, 2026

Commission File Number: 001-39570

TIM S.A.
(Exact name of Registrant as specified in its Charter)

João Cabral de Melo Neto Avenue, 850 – North Tower – 12^th floor
22775-057 Rio de Janeiro, RJ, Brazil
(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F ☒ Form 40-F ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1).

Yes ☐ No ☒

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7).

Yes ☐ No ☒

TIM S.A.

Publicly-Held Company

CNPJ/MF 02.421.421/0001-11

NIRE 333.0032463-1

MINUTES OF THE BOARD OF DIRECTORS’ MEETING

HELD ON JANUARY 21^ST, 2026

DATE, TIME AND PLACE: January 21^st, 2026, at 11.00 a.m., at the head office of TIM S.A. (“Company”), domiciled at Avenida João Cabral de Mello Neto, 850, Torre Sul, 13° floor, Barra da Tijuca, in the city and State of Rio de Janeiro.

PRESENCE: The Board of Directors’ Meeting of the Company was held at the date, time and place mentioned above, with the presence of Messrs. Nicandro Durante, Adrian Calaza, Alberto Mario Griselli, Alessandra Michelini, Claudio Giovanni Ezio Ongaro, Denísio Augusto Liberato Delfino, Flavia Maria Bittencourt and Gigliola Bonino, either in person or by means of audio or videoconference, as provided in the 2^nd paragraph of Section 25, of the Company’s By-laws. Justified absence of Messrs. Gesner José de Oliveira Filho and Leonardo de Carvalho Capdeville.

BOARD: Mr. Nicandro Durante – Chairman; and Mrs. Fabiane Reschke – Secretary.

AGENDA: (1) To resolve on the execution of contracts for the supply of Radio Access Network (“RAN”) goods and services; (2) To resolve on the execution of a unified infrastructure lease agreement between the Company and American Tower do Brasil – Cessão de Infraestruturas S.A. (“AMERICAN TOWER – ATC”).

RESOLUTIONS: Upon the review of the material presented and filed at the Company’s head office, and based on the information provided and discussions of the subjects included on the Agenda, the Board Members, unanimously by those present and with the abstention of the legally restricted, decided to register the discussions as follows:

(1) Approved the terms and conditions for the execution of agreements for the supply of goods and services of Radio Access Network (“RAN”) between the Company and suppliers HUAWEI do Brasil Telecomunicações Ltda. and NOKIA Solutions and Networks do Brasil Telecomunicações Ltda., and authorized the Company's Officers to negotiate and enter into documents that may be necessary, according to the material presented.

CONT. OF MINUTES OF THE BOARD OF DIRECTORS’ MEETING OF TIM S.A.

January 21^st, 2026

(2) Approved the execution of a unified infrastructure lease agreement between the Company and AMERICAN TOWER – ATC, according to the technical, financial and commercial conditions presented, and authorized the Company's Officers to negotiate and enter into documents that may be necessary, in the terms and conditions of the support material which is filed at the Company's head office.

Additionally, the Board Members acknowledged on the preliminary analyses and studies involving the Company's strategic projects.

CLOSING: With no further issues to discuss, the meeting was adjourned, and these minutes drafted as summary, read, approved and signed by all attendees Board Members.

I herein certify that these minutes are the faithful copy of the original version duly recorded in the respective corporate book.

Rio de Janeiro (RJ), January 21^st, 2026.

FABIANE RESCHKE

Secretary

SIGNATURES

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