USPS Postmarks and Mailed Tax Payment Timeliness

• On December 24, 2025, the United States Postal Service (USPS) clarified that postmarks show the date a letter is processed, NOT the date that it was mailed.
• To prevent late penalties, consider mailing important tax documents and payments several days before the deadline, using certified mail, requesting a manual postmark at the counter, or using a delivery service (e.g., FedEx) that provides proof of when mail is submitted.

Taxpayers who submit payments or filings via USPS should know about the USPS’s process related to postmarking, as postmarks are used to determine whether those payments and filings are considered “on-time.” On December 24, 2025, the USPS clarified that the date stamped on mail is based on when it is first processed at a postal facility, not when it was dropped in a mailbox or handed in at the post office. Therefore, a tax return or payment mailed on the due date could receive a later postmark – sometimes days later – which a tax office would view as "late."

To help avoid late penalties, the Treasurer’s Office recommends meeting your local tax and filing obligations online in CAPP, the Customer Assessment and Payment Portal. With a CAPP profile, you can also pay Utility bills, sign up for reminder emails, view your assessment and payment history, or set up automatic payments for your accounts at no charge through the Automatic Bank Debit (ABD) Program.

Alternatively, consider mailing important tax documents and payments several days before the deadline, using certified mail, requesting a manual postmark at the counter, or using instead FedEx or a similar delivery service that provides proof of the actual date the item was submitted for delivery.