How to Appeal Property Taxes in San Diego County, California (2026 Guide)

For a 2026 regular secured assessment in San Diego County, file between July 2 and Monday, November 30, 2026. The initial Assessment Appeal Application (BOE-305-AH) must have an original signature and can be filed by mail or in person only with the Clerk of the Board of Supervisors, Assessment Appeals, 1600 Pacific Highway, Room 402, San Diego, CA 92101-2471; there is no filing fee.

How assessments work in San Diego County

San Diego County’s 2026 assessed-value notice is tied to the January 1, 2026 lien date. The Assessor’s 2026 secured roll notice says it covers locally assessed real property as of January 1, 2026, and that values shown online reflect Assessor records as of June 30, 2026. The key question for most homeowners is not “what is my home worth today?” but what could it have sold for on January 1, 2026?

California’s Proposition 13 system applies here: your taxable value generally starts with purchase price or new-construction value, then can rise by no more than 2% per year unless there is a reassessment event. San Diego’s notice explains the three big events: change in ownership, new construction, or a temporary reduction when current market value falls below the adjusted Prop. 13 base-year value. That temporary market-decline appeal is commonly called a Prop. 8 / decline-in-value appeal.

For the 2026 regular roll, the State Board of Equalization’s county deadline list and San Diego’s Assessor notice both put San Diego County in the November 30, 2026 deadline group. The filing window opens July 2, 2026. Supplemental assessments are different: if your appeal is about a purchase or new construction supplemental bill, the usual deadline is 60 days from the mailing date shown on the supplemental notice or bill.

Whether you should appeal

Appeal only if you can show the Assessor’s value is too high for the correct date. For a 2026 decline-in-value case, use sales closed close to January 1, 2026—ideally similar homes in the same neighborhood, school area, view/lot condition, size, age, and condition. The San Diego Assessor’s FAQ notes that the Assessment Appeals Board will not consider a sale more than 90 days after the valuation date when valuing a regular or supplemental assessment, so late-spring 2026 comps may not help much.

Start with the Assessor before filing if time allows. San Diego’s filing guide says Assessor staff can explain the basis for the assessment and review your information; if the Assessor finds an error, you may not need a formal appeal. But do not let informal review push you past November 30, 2026. A timely formal appeal protects your rights.

San Diego does publish useful appeal data, but not a homeowner “win rate” or median reduction. The Assessor’s FY 2025-26 annual report shows 2024 real-property appeal activity: 1,514 residential appeals received, 174 residential cases completed, and $7,387,155 actual assessed-value reduction in completed residential cases. It also reports an average actual A.V. reduction of 1.80% for completed residential cases. Treat that as workload/context, not odds of winning; it includes only completed cases and is not a median.

Also check exemptions before assuming an appeal is the only savings route. San Diego County’s Homeowners’ Exemption reduces assessed value by $7,000, saving about $70 per year, and should show on your bill as “HOMEOWNERS.” A qualifying disabled veteran or unmarried surviving spouse may get much larger savings; San Diego’s Assessor describes the disabled veterans’ exemption as worth about $1,700 in savings in many cases. If you are 55+ and moving, review the Prop. 19 senior base-year transfer rules. If your home was damaged by fire, flood, earthquake, or another calamity, separate disaster/calamity relief may apply if damage exceeds $10,000 and you apply within 12 months.

Step-by-step how to file

1. Look up your 2026 assessed value. Use San Diego County’s 2026 Notification of Assessed Value / secured roll search. Confirm the parcel number, land value, improvement value, total assessed value, and exemptions.

2. Decide the appeal type. Most first-time homeowners are filing either Regular Assessment – value as of January 1 of the current year and checking Decline in Value, or filing a Supplemental Assessment appeal after a purchase/new construction notice. Base-year value appeals, escape assessments, penalties, and calamity reassessments have different boxes and deadlines.

3. Use the official form. The required form is BOE-305-AH, Assessment Appeal Application. San Diego’s PDF is labeled BOE-305-AH (P1) Rev. 12 (05-24), Assessment Appeal Application. Do not attach your hearing evidence to the application; the form instructions say evidence is presented at the hearing.

4. Enter a real opinion of value. In Section 4, put the Assessor’s roll value in Column A and your requested value in Column B. If you claim $875,000, be ready to defend $875,000 with comps—not just “Zillow says less.”

5. Choose whether it is also a refund claim. The application asks whether it is designated as a claim for refund. San Diego’s guide says checking “yes” lets the county automatically process a refund if you win, but it can shorten litigation timing if you later challenge an unfavorable decision. Most homeowners who are simply seeking a tax refund for an overassessment prefer the automatic-refund convenience, but read the instructions.

6. File by mail or in person. San Diego County says the initial Assessment Appeal Application must have an original signature and can only be received by mail or submitted in person. Mail or deliver it to: Clerk of the Board of Supervisors, Assessment Appeals, 1600 Pacific Highway, Room 402, San Diego, CA 92101-2471. Mailed applications are treated as received based on the USPS postmark; if there is no USPS postmark, the Clerk uses the actual receipt date. Do not rely on email for the initial application.

7. Use email/fax only for later forms. Additional forms—withdrawal, agent authorization, contact change, postponement/continuance, two-year waiver, 45-day notice waiver, and agreement to waive in-person hearing—may be submitted by fax or email. The Clerk lists AssessmentAppeals@sdcounty.ca.gov for questions and additional-form submission, and the hearings page lists 619-531-5777.

What happens after

The proper appeal authority is the San Diego County Assessment Appeals Board, administered by the Clerk of the Board of Supervisors and independent from the Assessor’s Office. The hearings page describes the boards as quasi-judicial bodies of three members appointed by the Board of Supervisors, with professional experience in real estate, appraisal, accounting, law, or similar fields.

After filing, San Diego’s guide says you should receive a confirmation postcard within about two weeks. You may request an exchange of information more than 30 days before the hearing; then both sides trade the evidence they plan to use. You will get at least 45 days’ notice of the hearing date, and you or your agent must confirm attendance at least 21 days before the hearing using the method in the notice.

At the hearing, the Assessor and homeowner present evidence, may question each other, and the board decides the taxable value. It is less formal than court, and you do not need a lawyer. But the board can increase, decrease, or leave unchanged the assessment, so do not file an aggressive low number you cannot support. If you and the Assessor agree before the hearing, a written stipulation can be submitted and you usually do not need to appear. San Diego also has an Agreement to Waive In Person Assessment Appeal Hearing form; ask the Clerk how that option will work for your case before assuming a paper-only process is available.

State law generally requires the hearing and final determination within two years of a timely application unless there is a waiver or exception. The board may announce a decision at the hearing or mail it later. If written findings of fact are important because you may go to Superior Court, request them before the hearing and pay the current San Diego fee: $413 per appeal.

Local tips

Use San Diego-specific evidence. The Assessor’s office keeps recent-sales information at branch offices and the main County Administration Center office at 1600 Pacific Highway, Room 103. Local agents can often provide cleaner comps by subdivision, view, canyon adjacency, coastal influence, HOA/Mello-Roos burden, and condition.

Remember that an assessment appeal changes value, not every line of the bill. The countywide tax is generally 1% of assessed value plus voter-approved bonded debt, and direct charges such as Mello-Roos or special assessments may not fall when assessed value falls. San Diego’s Treasurer-Tax Collector explains Prop. 13 as 1% plus voter-approved bonds and assessments, and the Tax Collector’s map-tax-clearance guidance uses 1.25% as the maximum San Diego County estimated tax rate for 1% plus voter-approved bonds.

Worked example: suppose your 2026 assessed value is $950,000, but three comparable sales support $875,000 as of January 1, 2026. A successful appeal reducing value by $75,000 would save about $750 at the 1% base rate. Using San Diego’s 1.25% maximum estimate for 1% plus voter-approved bonds, the savings estimate is $937.50 for that tax year, before considering fixed charges that do not adjust with value. A Prop. 8 decline-in-value reduction is temporary, so check the next year’s notice and appeal again if the Assessor restores the value above market.