The U.S. Postal Service is changing its postmark rules, effective in 2026. The postmark will now reflect the date mail is first processed by an automated sorting machine, not the date it was dropped off. This change, part of the 'Delivering For America' initiative to modernize infrastructure, could cause delays for time-sensitive mail like tax returns, bills, and ballots, potentially leading to late fees or penalties. USPS suggests mailing such items several days early or requesting a manual postmark.