Effective December 24, 2025, USPS adopted a final rule adding Section 608.11 to the Domestic Mail Manual regarding USPS postmarks. Machine-applied postmarks will generally reflect the date mail is first processed at a regional USPS processing facility, rather than the date an item is deposited at a local post office or mailbox.

As a result of changes in USPS procedures impacting postmark dates, the postmark date on mailed items may be applied days after the item is delivered to USPS. This may cause a return, payment, or other submission that was mailed on or before a statutory deadline to nevertheless receive a postmark dated after the due date.

Because federal and state tax filing deadlines are determined by the postmark date (not the date of deposit), these changes introduce new timing risks for filings and payments submitted by mail across all jurisdictions.

Under current USPS processing procedures, routine mailbox drop-off, including at after-hours post office slots, may no longer reliably produce a same-day postmark.

What This Means for You

The USPS changes alter a long-standing assumption relied upon by taxpayers — that depositing mail with USPS by the filing deadline will result in a timely postmark. Under the revised processing procedures, this assumption may no longer hold true.

Electronic filing and electronic payment remain the most reliable ways to ensure timely submission and confirmation. If mailing a return, payment, or other time-sensitive document, you may wish to obtain proof of mailing, such as:

• a manual USPS postmark obtained at a retail counter,
• a Certificate of Mailing,
• mailing via Certified Mail or Registered Mail, or
• another IRS-approved delivery service that provides documented proof of mailing date.

Please Note

If you are mailing any tax-related documents or other time-sensitive correspondence, we encourage you to allow extra time and consider using one of the proof-of-mailing options described above to help minimize the risk of penalties or interest associated with a late postmark.

For additional information refer to the USPS Postmarking Myths and Facts. If you have questions about filing or payment options, or would like to discuss alternatives to mailing, please contact our office.