04/11/2026
***Important Reminder***
If you are mailing anything to the IRS (or other places) where postmark date matters, get it hand stamped inside the post office! For added assurance, consider getting additional proof of mailing such as using certified mail options.
As of December 2025, USPS postmark may reflect the date mail is processed at a regional facility, not the day it is dropped off. Mail may be postmarked 1–2 days after deposit, risking late fees for deadlines. For guaranteed same-day postmarks, you must request a manual, in-person postmark at a post office retail counter.