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01/16/2026
USPS postmark changes impact timeliness of tax filings
Learn how USPS postmark changes could impact timely tax filings and what steps you should take.
Effective Dec. 24, 2025, the U.S. Postal Service (USPS) updated its postmarking procedures. USPS postmarks now reflect the date of the first automated processing at a regional postal facility rather than the date the letter or package was dropped off.
Why this matters
This means your mail could be processed and postmarked even several days after the mail was dropped off at a post office or mailbox. Because many federal and state laws define timely filing or payment based on the USPS postmark, filings or payments may be considered delinquent even if they were mailed on or before the deadline.
How to ensure timely filing for tax
We strongly recommend that any mailed correspondence to federal and state/local tax authorities be sent via certified or registered mail. We equally recommend you do this for any important mailing to a governmental authority. The date stamp on the certified or registered mail receipt should be stamped with the date by a USPS employee. If such a stamped receipt is not obtained, print out and retain the online USPS tracking history (available only for a limited time).
If certified or registered mail is not an option, certain designated delivery methods via DHL Express, FedEx, and UPS are other adequate options. If used, make sure to retain written proof of the mailing.
If regular mail is your only option, we recommend that you mail items early (at least five days prior to the deadline) to ensure ample time for postal processing or request a manual postmark from a USPS employee upon drop-off at a retail location. Recommended parallel supplemental evidence of timely mailing to be gathered includes such items as time-stamped photos of making the timely manual mailing and of the specific items being mailed.
The USPS also explicitly warns that customer-applied pre-printed labels (such as from Self-Service Kiosks, Click-N-Ship online postage, or meter strips) are not sufficient for timely mailing as these only show when the postage was printed – not when the USPS accepted the item.
Questions
Contact your engagement team for guidance on how these changes may impact your tax filings.
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Any advice contained in this communication, including attachments and enclosures, is not intended as a thorough, in-depth analysis of specific issues. Nor is it sufficient to avoid tax-related penalties. This has been prepared for information purposes and general guidance only and does not constitute legal or professional advice. You should not act upon the information contained in this publication without obtaining specific professional advice specific to, among other things, your individual facts, circumstances and jurisdiction. No representation or warranty (express or implied) is made as to the accuracy or completeness of the information contained in this publication, and CohnReznick, its partners, employees and agents accept no liability, and disclaim all responsibility, for the consequences of you or anyone else acting, or refraining to act, in reliance on the information contained in this publication or for any decision based on it.