37 CFR § 2.194
Identification of trademark application or registration
November 5, 2020
(a) No correspondence relating to a trademark application should be filed prior to receipt of the application serial number.
(b)
(1) A letter about a trademark application should identify the serial number, the name of the applicant, and the mark.
(2) A letter about a registered trademark should identify the registration number, the name of the registrant, and the mark.