Postal Service changes that might affect the timing of when postmarks are applied. Late-arriving ballots drove the rejectionsAccording to state data, 148,241 mail ballots were rejected in the June election, or a rate of 1.73% of all mail ballots. Advertisement AdvertisementIn raw numbers, that's up from the 2024 primary, when 108,982 mail ballots were rejected, or a 1.56% rate. "Ballots rejected due to lateness are caused primarily to being postmarked too late to count, not because they arrived too late to count," Alexander wrote in an email. Advertisement AdvertisementEarlier this year, California election officials urged voters to send their mail ballots early, warning that Postal Service changes could lead to slower mail service.