6-K

UNITEDSTATESSECURITIES AND EXCHANGE COMMISSION****WASHINGTON, D.C. 20549

FORM 6-K

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

Date of Report: March 30, 2026

Commission File Number: 001-39570

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

JoãoCabral de Melo Neto Avenue, 850 – North Tower – 12^th^ floor22775-057 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

Corporate Taxpayer's ID (CNPJ/MF): 02.421.421/0001-11

Corporate Registry (NIRE): 33.300.324.631

NOTICE TO THE MARKET

Filing of annual report on Form 20-F for the yearended on December 31, 2025

TIM S.A. (“Company”) (B3: TIMS3; NYSE: TIMB) hereby informs its shareholders and the market in general that it has filed its 2026 annual report (“Form 20-F”) for the calendar year ended on December 31, 2025, with the U.S. Securities and Exchange Commission ("SEC").

The Form 20-F is available for download on the Company's Investor Relations website, www.tim.com.br/ir, and, in addition, shareholders may receive a hard copy of the Form 20-F and the complete financial statements, free of charge, by requesting in the following email ri@timbrasil.com.br.

Any further information regarding the Form 20-F can be obtained by contacting Investor Relations Team and/or Mr. Vicente de Moraes Ferreira, Investor Relations Officer of TIM S.A. through the channels indicated above.

Rio de Janeiro, March 30^th^, 2026.

TIM S.A.

Vicente de Moraes Ferreira

Investor Relations Officer

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.