A postmark date is the official date on which the U.S. Postal Service imprints a postmark on an item of mail. The postmark date is an important record of when a piece of mail is sent. In some cases, a recipient requires that items be postmarked by a deadline.
Mailed federal tax returns are considered submitted as per the date of postmark. The typical postmark imprint includes the date, time and location where the item is sent. The post office uses three methods to apply postmarks. The processes are automated, mechanized and manual. Permit, metered and pre-canceled mail do not receive a postmark.