Effective Dec. 24, 2025, the U.S. Postal Service (USPS) clarified that a postmark generally reflects when mail is processed at a USPS facility, not when it is dropped off or accepted. This change may affect whether mailed tax documents are considered timely filed.
The IRS applies a strict mailbox rule, relying on the postmark date to determine timely filing. Because mail may now be postmarked days after it is mailed, documents sent on time could still be treated as late — potentially resulting in penalties, interest or missed elections.
What this means for you
This guidance is especially important for paper‑filed tax documents and other time‑sensitive correspondence that cannot be submitted electronically.
Recommended actions to help reduce filing risk:
- Use electronic filing and payment options whenever available
- Avoid placing deadline‑sensitive mail in USPS collection boxes close to due dates
- Do not rely on customer-applied pre-printed labels (e.g., from self-service kiosks or postage meters)
- Obtain proof of mailing for deadline‑driven documents
- Obtain a postage validation imprint (PVI) by paying for postage at the USPS retail counter
- Request a manual postmark at the USPS retail counter
- Send as registered or certified mail