If you send timely documentation or payments through the U.S. Postal Service (USPS), a recent update to the Domestic Mail Manual (DMM) may affect how and when you send your mail.

This DMM update specifically addresses postmarks, defining what constitutes a postmark, outlining the various types of Postal Service markings that are considered qualifying postmarks, and explaining the circumstances under which these markings are applied to mail. While this update is not a change to existing USPS operations or procedures or postmarking procedures, it’s an update aimed at clarifying how postmarks are used in connection with the mailing date to ensure that the public has a better understanding of this process.

In light of the 2025 tax season, we’re sharing what you need to know about this update and what it means for you.

What this update means

Postmarks are typically applied to mail at USPS processing facilities. As a result, the date on the postmark may be later than the actual date when the mail was first accepted by the Postal Service. This means that there can be a delay between when a customer drops off their mail or when it’s placed in their mailbox and when it receives an official postmark, which may affect the documentation of the mailing date.

If you pre-print a label using a self-service kiosk or purchase one online, it only indicates the date on which the postage was bought. These labels do not serve as proof that the mail was actually accepted by USPS on that date, as they lack an official USPS acceptance postmark.

To ensure that your mail is postmarked on time, especially if you are facing an upcoming deadline, it’s best practice to take your mail to a Post Office counter, where you can request a manual postmark at no charge at any Post Office, station, or branch. This service is available for up to 50 mail pieces per customer and ensures that your mail contains the correct acceptance date as a postmark and provides an accurate record of when the item was given to USPS. If you would like to have proof of mailing, you can purchase a Certificate of Mailing at the Post Office or pay to send the mail by registered or certified mail.