The Cook County Clerk’s Office has provided important information regarding the USPS Postmark changes and how that may affect vote by mail ballots. Effective January 1, 2026, the US Postal Service (USPS) changed how postmarks are defined. Postmarks now reflect the date mail is processed – NOT the date it is dropped off. Processing can occur days after the ballot is placed on the mail. In Illinois, vote by mail ballots must be postmarked by Election Day and received within 14 days. Because of this change, ballots mailed on or even several days before Election Day could still receive a late postmark and be rejected. Here is what the Cook County Clerk’s Office recommends you should do if you vote by mail: do not wait until the final days – or Election Day – to mail your ballot; OR bring your ballot to a post office as early as possible and request a postmark; OR, beginning March 2, voters may use one of the Cook County Clerk’s 55 secure mail ballot drop boxes available throughout suburban Cook County. Vote by mail remains a secure, reliable, and trusted method of voting. These recommendations are intended to protect voters from postal processing delays and ensure every eligible ballot is counted. USPS Postmark Change & Vote by Mail Ballots Flyer