California Assessment Appeal Guide

What a California assessment appeal can and cannot fix

The California State Board of Equalization explains that county property taxes are based on the assessed value set by the county assessor. If you disagree with that value, you should first discuss the issue with the assessor’s staff. If you cannot resolve it, you may have a right to appeal under specific rules and limits. You can start with the BOE’s assessment appeals page.

In every California county, the local board of equalization function is handled by either an assessment appeals board or the county board of supervisors. The board is separate from the assessor. Its job is to resolve value disputes between taxpayers and the assessor.

An appeal may help when the county value is wrong because:

• the assessor used the wrong square footage, lot size, property type, or condition;
• the market value on the correct valuation date was lower than the enrolled value;
• the assessor valued new construction too high;
• a change in ownership reassessment appears wrong;
• a supplemental, escape, penalty, or roll-change assessment appears wrong;
• your property was damaged and the reassessed value after a calamity appears wrong.

An assessment appeal usually does not fix these problems:

• you cannot afford the tax bill;
• you disagree with local tax rates, bonds, or how tax money is spent;
• you missed a homeowners’ exemption, disabled veterans’ exemption, or other relief application;
• your mortgage escrow payment changed;
• your tax bill rose because a special assessment or local charge was added.

If the issue is a missing exemption, look for the county assessor’s exemption process. If the issue is a late tax bill, contact the tax collector or treasurer. If the issue is the value used to calculate the tax, this guide is the right place to start.

The offices involved

California homeowners often get confused because several offices touch the same bill.

Step 1: Read the notice and check the property record

Before filing anything, find the exact value you are challenging.

Look for:

• the assessor’s parcel number, often called the APN;
• the tax year or fiscal year;
• land value;
• improvement value, meaning buildings and other taxable improvements;
• total assessed value;
• the notice date, mailing date, or postmark if you received a special notice;
• whether the value came from the regular roll, a supplemental assessment, new construction, a change in ownership, a calamity reassessment, or an escape assessment.

Then compare the county’s property record to your actual home. Look for simple facts. Is the living area wrong? Is the number of bathrooms wrong? Is the lot size wrong? Did the county include a pool, garage, addition, or improvement that does not exist? Did it miss serious damage or condition problems?

A record error does not always require a formal hearing. The BOE says assessor staff may be able to correct an error after reviewing relevant information. But talking with the assessor does not automatically protect your appeal deadline.

Step 2: Decide what kind of value problem you have

The deadline and evidence depend on the kind of assessment you are challenging.

Decline in value, often called Proposition 8

A decline-in-value appeal is for a year when your property’s current market value is lower than its factored base year value as of January 1. The BOE’s Proposition 8 decline-in-value page explains that this kind of reduction is temporary and is reviewed annually.

This matters for homeowners who bought near a market peak, live in an area where prices fell, or have a property condition issue that reduced market value. You are trying to show the value on January 1 of the year you are appealing.

A Proposition 8 reduction does not permanently reset your Proposition 13 base year value. If the market later recovers, the assessed value can rise by more than 2 percent while the property remains in decline-in-value status, but without a change in ownership or new construction it should not rise above the factored base year value. The BOE explains this in its property assessment information sheet.

Base year value after purchase or new construction

When a property changes ownership or new construction is completed, the assessor may establish a new base year value. If you think that value is wrong, you may be challenging the purchase-date value, the completion-date value, or the portion of value added by new construction.

This is different from a normal annual decline-in-value appeal. The valuation date may be the change-in-ownership date or the completion date of the new construction, not January 1.

Supplemental assessment

A supplemental assessment usually follows a change in ownership or new construction. The BOE’s Publication 30 says supplemental assessment appeals generally must be filed no later than 60 days after the mailing date printed on the notice or tax bill, or the postmark date, whichever is later.

Calamity, escape, roll change, or penalty assessment

Different appeal periods can apply to other notices. Publication 30 says calamity reassessment appeals generally must be filed within six months of the mailing date or postmark of the reassessment notice, whichever is later. The BOE sample instructions for BOE-305-AH also explain that roll change, escape assessment, and penalty assessment appeals have their own 60-day filing rules.

Step 3: Check the deadline before you keep researching

Do this early. It is easy to spend days gathering evidence and then discover the formal filing window closed.

For regular assessment appeals, California’s state tax calendar lists July 2 as the first day to file an application for changed assessment. The regular filing period runs to September 15 in counties where the assessor provides value notices by August 1 to all real property assessees on the secured roll. In other counties, the regular filing period runs through November 30. See the state property tax important dates.

The BOE’s 2026 filing-period request to counties also states that county clerks certify whether the last day is September 15 or November 30, and it explains ways an application may be considered timely, including in-person delivery by close of business, a United States Postal Service postmark, accepted commercial delivery proof, or e-filing where the county accepts electronic filing. See the BOE 2026 filing-period request.

Do not guess your county deadline. Use the current county clerk or assessment appeals board page. County deadlines are certified each year. A weekend or legal holiday can also affect the last valid day.

Step 4: Ask the assessor for an explanation, but do not miss the filing window

Many homeowners should contact the assessor before filing a formal appeal. Ask for the property record, the enrolled assessed value, and the reason for the value change.

A simple call or email may show that:

• the assessor has the wrong property facts;
• the value came from a recent purchase or construction permit;
• the property is already in decline-in-value status;
• an exemption issue, not an appeal issue, caused the bill to rise;
• the tax collector added penalties or charges unrelated to the assessed value.

Some counties offer an informal review or decline-in-value review. This can be useful. But it is not always the same as a formal appeal. Unless the county clearly says otherwise in writing, do not assume that an informal review preserves your formal appeal rights.

Step 5: Get the right county form

California uses BOE-305-AH, Assessment Appeal Application, but homeowners must use the county’s actual appeal application. The BOE’s assessment appeals guidance says you obtain form BOE-305-AH from the clerk of the board in the county where the property is located, and that you must use the county application for the appeal to be valid.

County pages can look different. For example, the Los Angeles County Assessment Appeals Board has its own online filing system. The Orange County Clerk of the Board posts appeal links, rules, forms, and hearing information. The San Diego County Clerk of the Board posts its assessment appeal application and filing instructions. These are examples only. Your county’s process controls your filing.

Local rule: Some counties charge filing or processing fees. Some offer fee waivers or different filing choices. Some allow e-filing. Some require signatures or mailed originals. Check the county clerk’s instructions before you submit.

Step 6: Build evidence that matches the valuation date

An appeal is not won by saying the bill feels too high. The board needs evidence of value.

Publication 30 says that, in most residential appeals, sales of properties similar to yours are usually the most reliable evidence of fair market value. These are often called comparable sales or comps.

Good evidence may include:

• three or more comparable sales, with addresses or APNs;
• sale dates and sale prices;
• living area, lot size, age, condition, bedroom and bathroom count, and major features for each comparable property;
• photos showing condition differences, location problems, damage, views, traffic, slope, or other factors;
• repair estimates for serious condition problems;
• an appraisal, if you have one and it matches the correct valuation date;
• purchase documents if the appeal involves a recent sale;
• permit, contractor, or construction records if the appeal involves new construction;
• the county property record showing any incorrect facts.

Match the evidence to the date. For a decline-in-value appeal, the valuation date is January 1 of the year being appealed. Publication 30 says comparable sales may be before January 1, but not more than 90 days after January 1 for a decline-in-value appeal. It also warns that using sales more than 90 days after the valuation date is a common error.

For a change-in-ownership appeal, use the date of the ownership change. For completed new construction, use the completion date stated on the reassessment notice. For calamity reassessment, use the date of the misfortune or calamity.

Step 7: File the appeal carefully

Use the county form. Fill in the parcel number, applicant information, mailing address, property type, assessment type, tax year, opinion of value, and reason for the appeal.

Keep copies of everything:

• completed appeal application;
• proof of mailing, delivery, or electronic filing;
• county confirmation number;
• payment receipt or fee waiver request, if any;
• all notices from the clerk or assessor.

Important: Filing an assessment appeal does not stop the tax bill from coming due. Publication 30 says you must pay property taxes on time even if an appeal is pending. If the appeal lowers the value, the county may issue a refund of taxes paid, with interest under the applicable rules.

Step 8: Prepare for the hearing

After you file, the county may schedule a hearing, contact you about missing information, or present a proposed stipulation if the assessor agrees to a value before the hearing. A stipulation is a written agreement on value. The board may accept or reject it.

If there is a hearing, organize your evidence in a simple order:

• what value the county used;
• what value you believe is correct;
• the valuation date;
• your best comparable sales or other valuation evidence;
• property record errors or condition problems;
• short explanation of how each item supports your number.

Do not assume the board will read documents you gave to the assessor earlier. Publication 30 says the board may consider only evidence presented at the hearing. Bring or submit evidence in the way your county rules require.

California also allows a formal exchange of information in certain situations. Publication 30 says an exchange is optional and may be requested by either side. If you request it after filing, you should send the request to the clerk and assessor before 30 days before the hearing, and the assessor must respond at least 15 days before the hearing. County local rules may add details, so check your hearing notice.

What happens at the hearing

The hearing is about evidence. The assessor or assessor’s representative may present the county’s value. You or your representative may present your opinion of value and evidence. The board may ask questions.

The board can decide to:

• leave the value the same;
• lower the value;
• raise the value if the evidence supports a higher value.

This is one reason to be careful before filing. The BOE warns that an appeals board is not bound by either side’s number. It must decide value based on the evidence.

Some counties use hearing officers for certain less complex cases. A hearing officer process may be less formal, but local rules decide whether the decision is final or only a recommendation. Ask the clerk how your county handles hearing officer decisions.

If you are late, denied, or confused

If you missed the regular filing period, call the clerk of the board and ask whether any deadline exception applies to your exact notice. Do not assume there is a late filing option. Many assessment appeal deadlines are strict.

If you missed a supplemental assessment appeal period, Publication 30 says you may still be able to appeal the new assessed value when it becomes part of the regular assessment roll, including in the year first placed on the regular roll or within the following three years. That does not necessarily reopen the closed supplemental assessment itself.

If your application was rejected as incomplete or invalid, ask the clerk what rule caused the problem and whether it can be corrected. Keep the answer in writing if possible.

If your appeal was denied because you missed the hearing, contact the clerk immediately. The BOE says some local boards have procedures to reconsider a nonappearance denial if you file a written request within the board’s deadline and show good cause. The time may be short.

If you disagree with the board’s final decision, the BOE says a challenge must be filed in county superior court within six months of the decision. That is a legal step. Consider speaking with a qualified attorney if you are thinking about court.

Appeal, exemption, rebate, credit, deferral, freeze, or postponement?

California homeowners often use these words together, but they are not the same.

Careful next steps

If your assessment looks wrong, do three things now.

• Save the notice, envelope, tax bill, and property record.
• Check the current county appeal deadline with the clerk of the board.
• Gather value evidence tied to the correct date before you file or attend a hearing.

Do not wait for an informal review if the formal deadline is close. Do not rely on a neighbor’s lower assessment without checking why it is lower. Under Proposition 13, similar homes can have very different assessed values because they were purchased at different times.