Burlingame and Hillsborough homeowners who think their 2026 property assessments are too high can challenge them without driving to Redwood City or mailing paperwork.
San Mateo County launched a new online portal that lets property owners file assessment appeals, pay the $30 application fee, upload supporting documents and track their case status around the clock. The county announced the portal on its verified government X account on Aug. 20.
The filing window opened July 2 and closes Monday, Nov. 30.
The county has said there are no extensions or exceptions to that deadline.
Why it matters locally
Burlingame ranked fifth countywide in assessed-value growth this year, adding $1.15 billion, according to a press release from San Mateo County Assessor Mark Church announcing the 2026-27 assessment roll hit a record $357.6 billion. The countywide median home sale price reached $2.2 million by May 2026.
The growth comes as some property owners may question whether their assessed values reflect current market conditions. In 2025, the Assessor's Office reviewed more than 7,400 properties for potential value declines and granted temporary reductions to 6,572 of them, totaling about $3.5 billion in relief.
How the portal works
Each application covers one parcel and one tax year. The $30 fee is non-refundable. Property owners who prefer paper can still mail or hand-deliver a signed application to the Assessment Appeals Board at 500 County Center, 5th Floor, BOS 104, Redwood City, CA 94063.
The three-member Assessment Appeals Board, appointed by the Board of Supervisors, hears evidence from both the property owner and the Assessor's Division. It can reduce, leave unchanged or increase the enrolled value. Property owners must keep paying their tax bills on time while an appeal is pending; if the board lowers the value, a refund or adjustment follows.
Separate informal option has an earlier deadline
Property owners can also request a free informal Decline in Value review directly from the Assessor's Division. That deadline is Oct. 31, one month earlier than the formal appeal cutoff. The two processes are separate: waiting for informal results does not protect formal appeal rights. Missing the Nov. 30 deadline means losing the right to formally appeal for the 2026 tax year.
"San Mateo County continues to demonstrate remarkable economic resilience and long-term stability," Assessor Mark Church said in a July 6 press release announcing the record roll. "This year's assessment roll growth reflects continued confidence in San Mateo County's future."
For questions, property owners can email the AAB Clerk at [email protected] or call (650) 363-4573.
