305.02(c) Location and Form of Certificate
The certificate of mailing: (1) must state the date of deposit in the mail, which must be a date within the set filing period (this includes the last day of the period, or the succeeding day that is not a Saturday, Sunday, or Federal holiday within the District of Columbia when the last day of the period falls on a Saturday, Sunday, or Federal holiday within the District of Columbia); and (2) should be signed by a person who has a reasonable basis to expect the correspondence to be deposited in the mail on the date indicated. 37 C.F.R. §2.197(a)(1). The signature of the certificate must be separate from any signature for the correspondence being deposited.
The best location for the certificate of mailing is at the beginning of the correspondence to which it pertains, typed in its entirety. The certificate of mailing should be separated from contents of the correspondence that are on the same page. Several blank lines between the contents and the certificate will suffice.
If the certificate of mailing does not fit on the correspondence to which it pertains, the certificate may be placed on a separate sheet of paper that is attached securely to the correspondence. The separate sheet must exhibit or bear a complete identification of the nature of the document or fee as well as an identification of the application, registration, and/or proceeding to which the document pertains (including serial number or registration number). The separate sheet may be a cover letter or transmittal letter, with the certificate placed at the bottom of the letter and signed separately from the letter. If there is any doubt concerning the correspondence to which a certificate of mailing on a separate sheet relates, the USPTO will not accept the certificate.
There must be a certificate of mailing for each piece of correspondence. When correspondence for more than one application or registration is mailed in a single envelope, each item of correspondence must have its own certificate of mailing. Similarly, when more than one type of correspondence is submitted in connection with the same application, each item of correspondence must have its own certificate of mailing.
It is suggested that the certificate be signed by the applicant or the party involved in the proceeding, or by the attorney for such person. If someone else signs, it should be a responsible person in a position to know that the mail will be deposited on the date specified.
The USPTO accepts the date of deposit stated in the certificate of mailing on the basis of the statement of personal knowledge. The USPTO does not normally inspect the postmark on the envelope.