Generate a California over-assessed property value challenge demand letter. Cite Prop 13, meet filing deadlines, and dispute your assessment with confidence.
Generate My Letter — $19If you believe your California property has been over-assessed, you have a constitutional and statutory right to challenge that valuation. Under Proposition 13 and California's Revenue and Taxation Code, your property's taxable value cannot exceed its fair market value as of the lien date (January 1). When a county assessor sets a value higher than what your property would sell for on the open market, you are entitled to seek a reduction through your county's Assessment Appeals Board. A well-drafted demand letter to the County Assessor often resolves the dispute informally, avoiding the need for a formal hearing. This page explains how California's assessment appeal process works, what deadlines apply, and how a properly worded challenge letter can help you reclaim overpaid property taxes.
California property tax law is governed by Article XIII A of the California Constitution (Proposition 13), which limits the ad valorem property tax rate to 1% of the property's assessed value and caps annual increases in assessed value at 2%, except when the property changes ownership or undergoes new construction. When a change in ownership occurs, the property is reassessed at its current fair market value, becoming the new 'base year value' under Revenue and Taxation Code § 110.1.
If the assessor's valuation exceeds the property's actual fair market value, the owner may pursue a 'decline-in-value' reduction under R&T Code § 51(a)(2), commonly known as a Proposition 8 reduction. This temporarily lowers the assessed value to reflect current market conditions when market value falls below the factored base year value.
The formal challenge process is set out in R&T Code §§ 1603-1605. A taxpayer files an Application for Changed Assessment with the county Assessment Appeals Board (or the Board of Equalization in smaller counties). The application must be filed during the regular filing period, which runs from July 2 through either September 15 or November 30, depending on whether the county mails assessment notices to all taxpayers. For supplemental or escape assessments, the deadline is 60 days from the mailing date on the notice.
The burden of proof generally rests on the taxpayer to show the assessor's value is incorrect, though the assessor bears the burden for owner-occupied single-family dwellings under R&T Code § 167. Evidence typically includes recent comparable sales, appraisals, income data for income-producing property, and documentation of physical defects or market decline. If the Board agrees the property is over-assessed, the value is reduced and the county must refund any overpaid taxes with interest pursuant to R&T Code § 5151.
A demand letter to the County Assessor is often the fastest, lowest-cost way to resolve an over-assessment in California. Before filing a formal Assessment Appeals Board application, many counties offer an informal 'Decline-in-Value Review' or 'Prop 8 Review' process in which the assessor's office will reconsider the value upon written request supported by evidence.
An effective letter should identify the property by Assessor's Parcel Number (APN), state the assessed value being challenged, and explain why that value exceeds fair market value as of the January 1 lien date. Attach supporting evidence: three to six comparable sales from within 90 days of the lien date, a recent appraisal if available, photographs of any deferred maintenance or damage, and for income properties, rent rolls and operating statements. Cite Proposition 13, R&T Code § 51(a)(2), and the assessor's duty to value property at the lesser of factored base year value or current market value.
The letter should request a specific reduced value, ask for written confirmation of any adjustment, and state your intent to file a formal Application for Changed Assessment under R&T Code § 1603 if the matter is not resolved before the filing deadline expires. Sending the letter via certified mail with return receipt creates a clear record. Even if the informal review does not produce the requested reduction, the letter and the assessor's response can be useful evidence at a later Assessment Appeals Board hearing and demonstrates good-faith efforts to resolve the matter.
Filing an Application for Changed Assessment with the county Assessment Appeals Board typically costs between $30 and $50, though some counties charge no fee. The Board must hear the appeal within two years of filing under R&T Code § 1604(c); if it does not, the taxpayer's opinion of value generally becomes the assessed value. You must continue paying property taxes while the appeal is pending to preserve refund rights. Adverse decisions can be challenged by filing a refund claim under R&T Code § 5097 and then a Superior Court action under § 5140. California small claims court (limit $12,500) generally cannot hear property tax assessment disputes, as exclusive jurisdiction lies with the Assessment Appeals Board and Superior Court.
Property tax in California is governed by the California Revenue and Taxation Code (property taxation), implementing Article XIII A of the CA Constitution (Proposition 13) (Cal. Const. art. XIII A (Prop 13); Cal. Rev. & Tax. Code §§ 110, 619, 1603, 3691 et seq.). Assessment cycle: Annual lien date of January 1 each year; under Prop 13 the base-year (purchase-price) value is set at acquisition and capped at a maximum 2% inflationary increase per year unless there is a change in ownership or new construction that triggers reassessment. Assessed value: 100% of full cash value (fair market value). Cal. Rev. & Tax. Code § 401 requires assessment at full value. Under Prop 13 the taxable value is the factored base-year value (acquisition value + 2%/yr max), not annual market value.
County Assessor (assessment) and county Assessment Appeals Board / county Board of Equalization (appeals) at the local level; the California State Board of Equalization (BOE) provides statewide oversight, guidance, and property tax rules. The window to act is short — regular assessment appeals filing period runs July 2 through either September 15 or November 30 depending on the county. As of 2025, 11 counties (incl. Alameda, San Francisco, Santa Clara, Ventura) use September 15; the other 47 counties use November 30. Supplemental and escape assessments must be appealed within 60 days of the notice/tax bill mailing date. No extensions.
A recent change to watch: Proposition 19 (passed Nov. 2020; base-year-value transfers effective April 1, 2021) lets homeowners 55+, severely and permanently disabled, or victims of wildfire/disaster transfer their Prop 13 base-year value to a replacement home anywhere in California up to three times, while narrowing the parent-child reassessment exclusion largely to a primary residence the transferee occupies.
How your value is assessed: 100% of full cash value (fair market value). Cal. Rev. & Tax. Code § 401 requires assessment at full value. Under Prop 13 the taxable value is the factored base-year value (acquisition value + 2%/yr max), not annual market value.
Evidence that works: Comparable sales, appraisals, income/expense data (income approach), cost data, and evidence of fair market value as of the valuation date; the § 110(b) rebuttable presumption is that full cash value equals actual purchase price in an open-market transaction.
Appeal deadline: Regular assessment appeals filing period runs July 2 through either September 15 or November 30 depending on the county. As of 2025, 11 counties (incl. Alameda, San Francisco, Santa Clara, Ventura) use September 15; the other 47 counties use November 30. Supplemental and escape assessments must be appealed within 60 days of the notice/tax bill mailing date. No extensions.
First-level appeal: Application for Changed Assessment filed with the clerk of the county Assessment Appeals Board (AAB), or in smaller counties the county Board of Equalization sitting as the appeals board (Cal. Rev. & Tax. Code § 1603).
Next-level appeal: After exhausting the administrative appeal before the Assessment Appeals Board, the taxpayer's further remedy is a refund action in California Superior Court (judicial review), typically after paying the tax and filing a refund claim; there is no intermediate second administrative appeal body.
Grounds you can raise: Assessor's full cash value (fair market value) exceeds actual market value; incorrect base-year value; decline-in-value (Prop 8) below the factored Prop 13 base value; improper change-in-ownership or new-construction reassessment; supplemental or escape assessment disputes.
Exemptions to claim: Homeowners' Exemption: $7,000 reduction in assessed value of an owner-occupied principal residence. Veterans' Exemption: up to $4,000. Disabled Veterans' Exemption: roughly $161,083 basic / $241,627 low-income for 2026 (inflation-adjusted). Property Tax Postponement (age 62+, blind, or disabled) and Prop 19 base-year-value transfers for homeowners 55+, severely disabled, or disaster victims. Prop 13 caps assessed-value growth at 2%/yr.
The hearing: In-person (and increasingly virtual) evidentiary hearing before the county Assessment Appeals Board; taxpayer and assessor present evidence and testimony, and the board renders a value determination.
First, application for Changed Assessment filed with the clerk of the county Assessment Appeals Board (AAB), or in smaller counties the county Board of Equalization sitting as the appeals board (Cal. Rev. & Tax. Code § 1603).
If that fails, after exhausting the administrative appeal before the Assessment Appeals Board, the taxpayer's further remedy is a refund action in California Superior Court (judicial review), typically after paying the tax and filing a refund claim; there is no intermediate second administrative appeal body.
Mind the deadline: regular assessment appeals filing period runs July 2 through either September 15 or November 30 depending on the county. As of 2025, 11 counties (incl. Alameda, San Francisco, Santa Clara, Ventura) use September 15; the other 47 counties use November 30. Supplemental and escape assessments must be appealed within 60 days of the notice/tax bill mailing date. No extensions.
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