Recent changes to how the U.S. Postal Service determines postmark dates introduce new timing risks for contracts, filings, and payments that rely on postmark-based deadlines. Companies should review their contracts and internal notice procedures promptly to avoid unintended defaults or missed deadlines.
 
What Changed
Under a final rule published in the Federal Register and effective December 24, 2025, USPS clarified that many postmarks, particularly machine-applied postmarks, reflect the date an item is processed at a USPS processing facility, not necessarily the date the item was deposited, accepted at a retail counter, or stamped internally by a mailroom.

As a result, there may be a gap of several days between when an item is mailed and the postmark date that ultimately appears on the envelope.
 
Why This Matters
Many legal, regulatory, and contractual deadlines rely on the U.S. postmark date, including:

• Tax returns and tax payments (which are deemed filed on the date of the U.S. postmark)
• Court and administrative filings
• Contractual notices governed by “mailbox rule” or similar provisions
• Rent payments, default notices, termination notices, and other time-sensitive communications

 As a result, a document mailed “on time” may receive a later postmark, potentially causing a missed deadline even where the sender acted diligently.
 
Contract Review Considerations
In light of this change, we recommend that companies review their contracts and standard forms, with particular attention to:

1. Notice provisions that deem notice effective upon mailing or based on postmark date
2. Clauses that require notice by a specific date but do not account for processing delays
3. Provisions that mandate USPS mailing without alternatives (e.g., courier, email, or personal delivery)
4. Default, termination, renewal, and cure provisions that rely on mailed notices for time calculations

Depending on the contract and risk profile, it may be advisable to:

1. Amend notice provisions to define effectiveness by receipt, not postmark
2. Expressly permit manual postmarks, private carriers, or electronic delivery
3. Add timing buffers for mailed notices
4. Update internal notice and escalation procedures to reflect the new USPS rules

Practical Mailing and Delivery Options
For any notice, filing, or payment where timing is critical, consider the following approaches:

• USPS manual postmark: Mail must be taken directly to a USPS retail counter and a manual postmark must be explicitly requested (it is not automatic). Manual postmarks are provided free of charge for up to 50 pieces per visit. Mail cannot simply be dropped off.
• Proof of mailing: A Certificate of Mailing may be purchased at the time of mailing (currently $2.40 per item) to preserve evidence of the postmarked date.
• Certified or Registered Mail: Provides documented proof of mailing and delivery.
• Private delivery services: Certain private carriers provide independently verifiable mailing dates and are accepted for specific legal and tax filings.

Selecting the appropriate delivery method should be coordinated with the applicable contract language and deadline requirements.
 
Key Takeaway
The USPS postmark rule change introduces new timing risk for contracts and filings that rely on postmark dates. Proactive contract review and procedural updates can help mitigate exposure and avoid unintended defaults or missed deadlines.

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