The Mailbox Rule in 2026
What actually is a postmark?
Clarification on exactly what information a Postmark conveys is addressed in a recent, final rule from the US Postal Service.
As we exit the time warp that was the last two weeks, the first full week of January seems a perfect moment to revisit the concept of dates and measuring time.
On December 24, 2025, the USPS final rule went into effect, in part clarifying what a postmark is and what information it conveys. Many have experienced the impact of recent consolidation and changes in USPS operation under the Delivering for America Plan, with some reporting slower processing and delivery times than previously experienced.
The date a letter is delivered to a USPS receptacle, the date the letter is received by a USPS facility, and the date a letter is postmarked, are all events that may trigger a starting date for measuring time and they may each be different dates. Applications, contracts, and various laws often seek to measure time keyed off of an event’s date, an event date that theoretically should be easy to answer and reach consensus amongst the parties.
There are a number of options available to document the date the piece of mail is deposited with USPS, including requesting manual postmark (hand cancellation) and the option to purchase a certificate of mailing, which are all in addition to using alternative USPS services or non-USPS options.
We cannot assume that a piece of mail will be postmarked the same day it is picked up by USPS, so review any specific requirements that you need to meet, and plan accordingly.
USPS FAQs Changes in Service Standards