April 9, 2026— The Illinois Department of Revenue is reminding taxpayers of recent postal service changes that could affect tax filing deadlines in 2026.
Officials say updated procedures from the United States Postal Service mean postmarks may reflect when mail is processed rather than when it is dropped off. The change could impact time-sensitive documents, including tax returns and payments due April 15.
State revenue officials are encouraging taxpayers who plan to mail returns to send them earlier than usual to avoid delays. They also recommend requesting a manual postmark at a postal location, which reflects the date the mail is accepted.
Taxpayers may also deliver returns in person at department offices, where documents will be date-stamped as proof of receipt.
Officials say filing electronically remains the most reliable option to meet the deadline, noting that online filing and payment tools are available at no cost.
The department says planning ahead and using available options can help ensure returns and payments are submitted on time.
