New USPS postmark rule explained: Why mailing your tax return on April 15 could lead to IRS penalties

IRS tax return mailing deadline: Taxpayers filing by April 15 face new risks with United States Postal Service postmark changes. Effective December 24, 2025, postmarks may not reflect the actual drop-off date. This impacts the IRS mailbox rule, which uses the postmark for timely filing. Mailing on April 15 could result in a later postmark date. Early mailing or manual postmarks are recommended.