The U.S. Supreme Court will hear arguments Monday in a case challenging the practice of counting mail ballots that arrive after Election Day, a procedure currently allowed in 14 states with grace periods ranging from one day to three weeks.

The Republican National Committee and the Libertarian Party of Mississippi filed the lawsuit against Mississippi Secretary of State Michael Watson, arguing that federal Election Day statutes require all ballots to be cast on a single day. Mississippi's current law allows ballots to be counted if received within five days after the election. The challengers contend that such grace periods violate federal law, while supporters argue states have constitutional authority to set their own voting procedures.

The 14 states with grace periods for regular ballots currently accept mailed ballots for varying timeframes, from one day in Texas to 21 days in Washington state. An additional 29 states allow late arrival of military and overseas ballots. In Washington, 127,000 ballots were received after Election Day in 2024, according to state election officials.

Anticipating a potential adverse ruling, several states have already modified their laws. Ohio, Kansas, North Dakota, and Utah eliminated grace periods last year, while Minnesota shortened its deadline. Ohio Governor Mike DeWine said the Mississippi lawsuit forced his state to act preemptively despite his preference for maintaining the grace period.

Election officials and voting rights groups have warned that eliminating grace periods could create confusion and disenfranchisement, particularly given recent changes to U.S. Postal Service processing that may affect delivery times. They argue that states need flexibility to balance election security with practical voting access, especially for voters in rural areas or those relying on mail service.

A 2025 Brookings Institution study found mail voting to be secure, with approximately four fraud cases per 10 million mail ballots. About 30% of voters used mail ballots during the 2024 presidential election. The Supreme Court's decision could significantly impact voting procedures for this fall's midterm elections, with absentee ballots scheduled to be distributed in the coming months.