Also, the postmark will only count toward your benefit if it's a U.S. Postal Service postmark. ... This isn't recommended if you need to mail something to the IRS; doing so won't get the sender's receipt postmarked, and it will make it difficult to prove timely mailing if necessary.

Does IRS go by postmark date?

Your return is considered filed on time if the envelope is properly addressed, has enough postage, is postmarked, and is deposited in the mail by the due date. If you file electronically, the date and time in your time zone when your return is transmitted controls whether your return is filed timely.

Does the IRS verify every tax return?

The IRS does check each and every tax return that is filed. If there are any discrepancies, you will be notified through the mail.