37 C.F.R. § 2.160

(a) During the following time periods, the owner of the registration must file an affidavit or declaration of continued use or excusable nonuse, or the registration will be cancelled:

(1)(i) For registrations issued under the Trademark Act of 1946, on or after the fifth anniversary and no later than the sixth anniversary after the date of registration; or

(ii) For registrations issued under prior Acts, on or after the fifth anniversary and no later than the sixth anniversary after the date of publication under section 12(c) of the Act; and

(2) For all registrations, within the year before the end of every ten-year period after the date of registration.

(3) The affidavit or declaration may be filed within a grace period of six months after the end of the deadline set forth in paragraphs (a)(1) and (a)(2) of this section, with payment of the grace period surcharge per class required by section 8(a)(3) of the Act and § 2.6.

(b) For the requirements for the affidavit or declaration, see § 2.161.