In August of this year, the US Post Office announced a new rule that included a MAJOR change in when letters are postmarked. Under this new rule, most letters will no longer be postmarked on the day the letter is received by a post office but instead postmarked a day later when the letter is processed at a regional mail processing facility. It is vital that taxpayers mailing their payment on or shortly before the due date request and physically witness the hand-stamping of the postmark at the Post Office.