How USPS Postmark Updates May Affect Mail Deadlines in 2026

If you rely on postmarks for tax returns, payments, or other time-sensitive mail, you’ve likely learned that the U.S. Postal Service (USPS) clarified its procedures for dating mail. In December 2025, USPS announced letters and packages would be postmarked with the dates they were processed at a postal facility, not necessarily the date they were mailed. According to the USPS statement published January 2, 2026, Postmarking Myths and Facts, this is consistent with how USPS has applied postmarks for years.  

The key takeaway is that a postmark confirms USPS had the mail in its possession on the date shown, but that date may not reflect the moment you dropped the item off at a post office or collection box. As USPS continues to optimize transportation, some items may reach a processing facility a day or more after you mailed them, making the postmark date differ from the drop-off date.  

What Changed to USPS Postmark Practices?  

According to USPS, postmarking practices have not changed. It clarified them in the Domestic Mail Manual by adding Section 608.11, Postmarks and Postal Possession, a final rule issued November 24, 2025, and effective December 24, 2025. 

The announcement clarifying the procedure comes as part of the USPS Delivering for America plan, which was published on March 23, 2021. The strategies and initiatives USPS describes in the plan are meant to improve financial stability, service, and investment in USPS.  

I Have Time-Sensitive Mail; How Can I Be Sure it Will Be Dated Correctly? 

If you’re used to waiting until the day before a deadline to mail anything time-sensitive, you may want to rethink dropping it in the mailbox or post office drop box. Instead, choose one of these options if your mail must be postmarked the day you drop it off: 

• Request a manual postmark. Go inside the post office and request a manual postmark to ensure the date matches when your letter or package was accepted. Manual postmarks (also known as local postmarks) are free. 
• Purchase proof of acceptance. By sending your letter or package as Certified Mail, you have a receipt guaranteeing when your parcel was accepted and, if you choose to pay for it, delivery confirmation for important documents.  

If you need to drop mail in a mailbox or post office drop box, do not wait until the day of or the day before a deadline to do so. Instead, mail it a few days before the deadline to ensure it will be processed in time.  

Moving Forward 

USPS will postmark mail at a processing facility, and it may not be postmarked the day you mail it. Tax returns, payments, Social Security applications and forms, Medicare paperwork, and mail-in ballots will be affected by this rule clarification. To be certain your mail is processed in a timely manner, you must mail it several days before a deadline or take it to the counter to receive a manual postmark or send it as Certified Mail.