Beginning December 24, 2025, the United States Postal Service (USPS) quietly implemented significant updates to how postmarks are defined and applied. These changes directly affect taxpayers who plan to mail their tax returns to avoid e-filing fees and may inadvertently put them at risk of late filing penalties if they rely on old assumptions about postmark timing.
As a tax preparer, understanding these changes is essential so you can properly advise your clients before they drop a return in the mailbox thinking they're “safe” on a deadline day.
According to the USPS’s updated Domestic Mail Manual, the postmark date now reflects the moment the envelope is first processed by an automated USPS sorting facility, not the moment the taxpayer hands over the envelope or drops it off.
In practice, this means:
As a tax preparer, understanding these changes is essential so you can properly advise your clients before they drop a return in the mailbox thinking they're “safe” on a deadline day.
What changed with USPS postmarks?
Historically, if taxpayers deposited their tax return in a mailbox or handed it to USPS on the due date, the postmark would reflect that day. This is no longer the case.According to the USPS’s updated Domestic Mail Manual, the postmark date now reflects the moment the envelope is first processed by an automated USPS sorting facility, not the moment the taxpayer hands over the envelope or drops it off.
In practice, this means:
- A return dropped in a mailbox on April 15 could be sent to a regional processing center and not receive a postmark until April 16 or later.
- Local offices and collection boxes are no longer tied to same-day postmark expectations.
- USPS explicitly warns that the postmark date may not match the date the customer mailed the item, due to transportation delays and consolidated processing operations.
