305.02(e) Effect of Certificate of Mailing
The filing date assigned to paper correspondence is the date of actual receipt in the USPTO. 37 C.F.R. §2.195(a). The USPTO does not retain the envelopes in which material is received or record the date of the postmark.
The date of deposit indicated on the certificate of mailing is used only to determine whether the correspondence was deposited with the USPS within the filing period. See 37 C.F.R. §2.197(a). Therefore, if the correspondence is actually received in the USPTO within the filing period, the certificate of mailing is ignored. If, however, the USPTO receives the correspondence after the filing period has expired, the USPTO looks to see whether a certificate of mailing was included. If no certificate is found, the correspondence is untimely.
When a document received after the expiration of the filing period includes a signed certificate of mailing, and the date of deposit on the certificate is within the filing period, the USPTO considers the correspondence to be timely filed.
If the filing period ends on a Saturday, Sunday, or Federal holiday within the District of Columbia, the correspondence is considered timely if the date of deposit on the certificate of mailing is the next succeeding day that is not a Saturday, Sunday or Federal holiday within the District of Columbia (see 37 C.F.R. §2.196; TMEP §308).
Whenever it is necessary to change the effective filing date of an application (e.g., when an application filed under §1(b) of the Trademark Act is amended to request registration on the Supplemental Register after submission of an allegation of use), the date of actual receipt rather than the date on the certificate is the new effective filing date. See TMEP §§206–206.04 regarding changes in the effective filing date of an application.