Walnut Creek voters planning to mail their Nov. 3 ballots should do so no later than Oct. 23, Contra Costa County election officials recommend, as a new report documents rising late-ballot rejections across California.

The share of vote-by-mail ballots rejected as late jumped to 1.1% in the 2026 California primary, up from 0.3% in the 2024 general election, according to the Public Policy Institute of California. Those figures include vote-by-mail ballots returned by any method. The report defines late ballots as those postmarked after Election Day or received more than seven days afterward.

Nearly 90% of California voters cast ballots by mail in June, KQED reported. That includes voters who returned their mail ballots in person.

The United States Postal Service’s Regional Transportation Optimization program has eliminated evening pickup in some ZIP codes far from processing facilities. PPIC says mail deposited after morning collection in affected areas can receive a postmark the following day.

In December 2025, USPS clarified that a postmark does not necessarily reflect the date it first received a piece of mail. The agency says the clarification did not change its postmarking practices. Under California law, mail ballots must be postmarked on or before Election Day and received within seven days to count.

PPIC found that ZIP codes affected by the transportation program saw rejection rates climb 0.6 percentage points more than comparable ZIP codes between 2024 and 2025. That accounted for about 19% of the total statewide increase in late-ballot rejections between those elections. The institute concluded the overall rise cannot be pinned entirely on USPS changes.

Young voters had the highest rejection rate. Among voters who returned ballots through the mail aged 18 to 24, the rate reached 3.1% in the 2025 special election. For voters 65 and older, it did not exceed 0.5%.

Contra Costa County mailed ballots to all active registered voters on Monday, Oct. 5. Clerk-Recorder and Registrar of Voters Kristin B. Connelly said in the announcement: “We encourage Contra Costa voters to complete their ballot as soon as they receive it in the mail and get it back to us early.”

Kim Alexander, president of the nonpartisan California Voter Foundation, told KQED that mail now takes a longer route because of processing facility changes. In some counties, election mail travels to a processing center in Nevada before returning to California.

California Secretary of State Shirley Weber and Attorney General Rob Bonta have urged voters to mail ballots at least a week before Election Day, according to KQED. Weber’s office also recommends that anyone mailing a ballot on Election Day itself get a hand-stamped postmark from a postal employee inside a post office rather than dropping it in a collection box.

The county Elections Division recommends mailing ballots no later than Oct. 23 to ensure they arrive in time. Voters who want their ballot included in election-night results should ensure the county receives it by Friday, Oct. 30.

Voters can bypass USPS entirely by using one of Contra Costa County’s 43 official ballot drop boxes. Ballots must be dropped off by 8 p.m. on Election Day. Locations are listed on the county’s official drop-box page. Voters can also drop off their ballots at the county’s in-person voting locations. Ballots should be sealed in their signed return envelopes.

Voters who have not received their ballot by Oct. 19 should call 925-335-7800 or email the Elections Division at [email protected]. Ballot tracking is available through the Secretary of State’s “Where’s My Ballot” service.