The U.S. Postal Service is giving a critical warning to Americans looking to vote by mail in the 2024 presidential election.

USPS issued the advice to give the mail system a week to process ballots despite the agency so far sorting and delivering election mail quickly and on time. Sending ballots in by Oct. 29 would virtually eliminate any risk of them arriving late, however, as the Postal Service has so far this month delivered 99.9% of ballots on time.

As more Americans vote through paper ballots, election officials have been working to make sure those ballots arrive on time and securely.