Be Aware of USPS Change to Postmark Procedures
If you mail a time sensitive payment or document, be aware that it may not get a postmark until days after you put it in the mail. That could result in late charges or a missed deadline. See the USPS statement below.
“The Proposed Rule further advised that, while the presence of a postmark on a mailpiece confirms that the Postal Service was in possession of the mailpiece on the date of the postmark’s inscription, the postmark date does not inherently or necessarily align with the date on which the Postal Service first accepted possession of the mailpiece.”
Read the full notice on the USPS website: Federal Register :: Postmarks and Postal Possession