The new USPS postmark rule took effect on December 24, 2025, where postmarks are now applied at regional sorting facilities, which means the date stamped is when the processing begins, not when an item is mailed.
Items like tax payments (first installment due by January 31) that rely on postmark dates for deadlines can be impacted by later postmarks and risk penalties or delinquency.
Please note that time-sensitive mail should be mailed several days in advance to ensure it is received by any applicable deadlines.