What is the difference between the Certificate of Mailing and Priority Mail Express procedures?

While both the Certificate of Mailing (37 CFR 1.8) and Priority Mail Express (37 CFR 1.10) procedures can be used to establish timely filing of USPTO correspondence, they have some key differences:

• Certificate of Mailing can be used with any class of mail, while Priority Mail Express is a specific USPS service.
• Certificate of Mailing uses the date of deposit with USPS as the filing date, while Priority Mail Express uses the date of deposit as shown by the “date accepted” on the mailing label.
• Certificate of Mailing cannot be used for new patent applications, while Priority Mail Express can establish a filing date for new applications.
• Certificate of Mailing requires a signed certificate, while Priority Mail Express requires the mailing label to be affixed to the correspondence.

The MPEP notes: “New patent applications filed in accordance with 37 CFR 1.10 will be stamped by the Office with the date of deposit as Priority Mail Express® with the United States Postal Service.”

Both procedures have specific requirements and limitations, so it’s important to consult the full text of 37 CFR 1.8 and 37 CFR 1.10 when deciding which to use.