The overwhelming reason was simple: the ballots arrived too late to qualify under California law.
State records show that 93,479 ballots were rejected because they failed to satisfy the state’s deadline requirements. California allows mail ballots to arrive as many as seven days after Election Day, provided they are postmarked no later than Election Day itself.
Election officials believe many of the rejected ballots carried postmarks showing they were processed after Election Day, making them ineligible even if they physically arrived within the state’s extended acceptance window.
Kim Alexander, president of the nonpartisan California Voter Foundation, argued that the real issue may not be when ballots reached election offices but when the Postal Service officially processed them.
“Ballots rejected due to lateness are caused primarily to being postmarked too late to count, not because they arrived too late to count,” Alexander said.
That distinction has drawn increased attention to operational changes implemented by the U.S. Postal Service.
Election experts have questioned whether recent adjustments to postal processing may have unintentionally contributed to the higher rejection numbers. Earlier this year, a group of mostly Democratic senators raised concerns with Postal Service leadership, warning that changes to mail processing could affect election mail during future federal contests.
Under updated procedures, postmarks may now reflect when mail is processed at larger regional facilities rather than when voters first place ballots into the mail stream. Because several processing operations have been consolidated, critics worry that ballots mailed on time could receive postmarks after Election Day.
Those concerns prompted California election officials to urge voters well before the primary to return their ballots as early as possible rather than waiting until the final days before the election.
Some observers believe the highly competitive gubernatorial primary also encouraged many Californians to hold onto their ballots until late in the campaign, increasing the likelihood that thousands would miss the postmark deadline.
Late ballots were not the only reason votes failed to count.
State data shows roughly 44,000 ballots were rejected because election workers determined the signatures on the ballot envelopes did not match signatures already on file with election offices.
Another 8,300 ballots were rejected because voters failed to sign the return envelope altogether, making the ballots ineligible under state law.
Officials also reported that 743 ballots were rejected because those voters had already cast another ballot. Additional rejected ballots involved return envelopes that contained no ballot inside or multiple ballots submitted together in a single envelope.
The rejection rates also varied significantly across California counties.
Tulare County recorded the state’s highest rejection rate, with 3.52% of returned mail ballots rejected. Alpine County and Merced County followed closely behind, each posting rejection rates of 3.36%.
The latest numbers are likely to intensify criticism of California’s election system, which routinely takes weeks to certify election results because state law permits qualifying mail ballots to continue arriving after Election Day.
President Donald Trump again criticized California’s election procedures following the June primary, arguing the state’s voting system requires significant reform. Meanwhile, the Department of Justice has opened an investigation into election administration in Los Angeles County, adding further attention to how elections are conducted in the nation’s most populous state.
At the same time, election experts caution against interpreting the increase in rejected ballots as evidence of widespread election fraud.
A 2025 study from the Brookings Institution concluded that documented cases of mail ballot fraud remain exceedingly uncommon, estimating roughly four fraudulent cases for every 10 million mail ballots cast. The Associated Press likewise reported that state officials have not identified evidence linking the rejected ballots to widespread fraud.
Instead, officials are expected to spend the coming months examining whether postal processing changes, voter behavior, or election procedures played the biggest role in the increase.
Regardless of the final conclusions, the June primary has once again placed California’s vote-by-mail system under a national spotlight. While state leaders continue promoting expanded access to voting, the sharp rise in rejected ballots is certain to fuel additional debate over whether the system is delivering both accessibility and confidence in the electoral process.
