More than a third of the 148,000 rejected mail-in ballots from California’s June primary were discarded because they were postmarked late, which experts largely attribute to a recent change in the US Postal Service’s postmarking policy.

As the Associated Press reports, nearly 150,000 California mail-in ballots were rejected in the June primary, with many arriving with postmarks that made them ineligible to be counted. Voting experts say the increase appears to be tied in part to recent US Postal Service changes that can delay when a mailpiece receives its postmark.

California allows mail ballots to be counted if they are postmarked by Election Day and arrive within seven days afterward, but experts say the issue is that some ballots are now receiving a postmark date based on when they are processed rather than when they were handed over to the Postal Service.

The state’s rejection rate in June was reportedly 1.73%, with 148,241 ballots rejected out of all returned mail ballots. That was higher than recent primary elections, including 2024, when 108,982 ballots were rejected, or about 1.56%. According to the AP, late arrival was by far the most common reason ballots were discarded — more than 93,000, followed by nearly 44,000 ballots where the voter’s signature did not match county records and more than 8,300 returned without a signature altogether.

Kim Alexander, president of the nonpartisan California Voter Foundation, said the problem is largely related to postmark timing rather than ballots simply arriving too late.

“Ballots rejected due to lateness are caused primarily to being postmarked too late to count, not because they arrived too late to count,” Alexander told the AP in an email.

Per the Postal Service’s new policy, customers can request a postmark on the same day it is mailed by dropping it off a Postal Service retail counter. The service is free, but many voters are unaware that they must specifically request one.

Without a manual postmark, the date applied to a ballot’s envelope may reflect when the mail is processed at a sorting facility rather than the day it was accepted by the Postal Service. Recent Postal Service consolidations have also reportedly moved some processing centers farther from communities, potentially adding delays before a postmark is applied.

California election officials warned voters earlier this year to mail ballots early or drop them off at polling stations because of concerns that Postal Service changes could affect delivery times.

The rejected ballots became fuel for a broader political fight after late-counted ballots shifted some election results weeks after Election Day.

President Donald Trump reportedly criticized California’s counting process, while state officials said the extended counting period is required under state law to allow counties to verify and count eligible ballots.

The site Rolling Out recommends that voters utilize the state’s free BallotTrax tracking system to make sure their votes were counted. Researchers reportedly found that voters who do not sign up are more likely to have ballots rejected, largely because they may not learn about signature issues in time to correct them.

Related: SF Election Turnout Looking Historically Low, and Why Does No One Vote on Election Day Anymore?

Image: In this photo illustration, the envelope holding an official ballot,  mailed to a Southern California resident, ahead of a state primary  election, photographed May 5, 2026 in Los Angeles, California. Every  registered voter in California will receive a ballot by mail. (Photo  Illustration by Jay L Clendenin/Getty Images)