Does the US Postal Service always postmark an election ballot on the day it is mailed?
No.
The U.S. Postal Service adopted a rule effective Dec. 24 clarifying that some mail is not postmarked when it is first received – at a post office, for example – but rather on a later date, during processing.

The rule doesn’t change practices, but instead is “intended to improve public understanding of postmarks and their relationship to the date of mailing.”
Postmarking can affect whether local officials accept election ballots.
Fourteen states accept a mailed ballot if it is received after Election Day, as long as it is postmarked on or before Election Day. Thirty-six states, including North Dakota, require absentee ballots, including those cast by mail, to be received by the local election office by Election Day.
Manual postmarks can be requested at post offices.
The postal service has been reducing operations, increasing postmarking delays, the Brookings think tank reported.
This fact brief is responsive to conversations such as this one.
This fact brief was originally published on Wisconsin Watch, a Gigafact partner.

Sources
- Federal Register: Postmarks and Postal Possession
- National Conference of State Legislatures: Receipt and Postmark Deadlines for Absentee/Mail Ballots
- Brookings: When a postmark no longer tracks mailing
- Wisconsin Elections Commission: Vote Absentee By Mail
- Washington Post: Thousands of mail-in ballots could be discounted under new post office policy
- San Francisco Chronicle: USPS quietly changes how postmarks work — and it could affect mail-in ballots