California property tax starts with the county assessor's valuation

Your property tax bill in California comes from a formula: the county assessor sets a value for your property, then applies a tax rate to that value. The base rate is 1% of assessed value, plus any voter-approved local bonds or assessments. The assessor's valuation is the number that moves most, so understanding how they arrive at it explains most of your bill.

The assessor in your county (not the state) does this work. They maintain records on every parcel, track sales prices when properties change hands, and adjust values based on market conditions and property characteristics. You receive a notice of assessed value each year, usually in the fall, before your bill arrives.

California's Proposition 13, passed in 1978, limits how fast assessed value can rise. Your property is reassessed at market value only when it sells. Between sales, the value can increase no more than 2% per year, even if the market rises faster. This is the single largest factor shaping your tax bill over time.

Key Takeaways

  • The county assessor determines your property's assessed value, which is multiplied by 1% plus any local assessments to produce your tax bill.
  • Proposition 13 caps annual value increases at 2% unless the property sells, meaning your tax can stay far below market value for decades.
  • The assessor uses comparable sales, income approach for rentals, and cost approach for new construction to set initial values.
  • You receive a notice of assessed value each fall and can file a written appeal within 30 days if you believe the value is wrong.
  • Supplemental bills appear when property changes ownership or new construction is completed, reflecting the new assessed value.

How the assessor values your property

The assessor uses three main methods, depending on the property type. For single-family homes and most residential property, the sales comparison approach is standard: the assessor looks at recent sales of similar homes in your area and adjusts for differences in size, condition, location, and features. If your home is similar to one that sold six months ago for $800,000, and yours has an extra bedroom, the assessor might value yours at $850,000.

For rental properties and income-producing land, the assessor uses the income approach. They estimate the annual rental income the property generates, subtract operating expenses and a vacancy allowance, then divide by a capitalization rate to arrive at value. A duplex that nets $30,000 per year might be valued at $600,000 if the cap rate is 5%.

For new construction, the assessor uses the cost approach: the land value plus the cost to build the structure, minus depreciation. This method is also used when comparable sales are scarce or the property is unusual.

The assessor's office is public. You can visit or call your county assessor's office to see what data they used for your property. Many counties now post assessment information online, including the assessed value, property description, and the comparable sales or method used.

Proposition 13 and the 2% annual cap

Once the assessor sets an initial value, Proposition 13 limits how much it can grow. Each year, the assessed value can increase by up to 2%, compounded. It cannot increase faster than that unless the property sells or new construction is added.

This means a home assessed at $500,000 in 2015 would be capped at approximately $552,000 in 2024, even if the market value is $900,000. The gap between assessed value and market value can be enormous, especially in fast-appreciating areas. When you eventually sell, the new owner's assessed value resets to the sale price, and the 2% cap starts over for them.

New construction is reassessed at completion, not subject to the 2% cap initially. If you add a room or major improvement, the assessor may increase your value to reflect the addition. The increase applies only to the added value, not your whole property.

When your property is reassessed

A change in ownership triggers a full reassessment. This includes a sale to a new owner, transfer to a family member (with some exceptions), or transfer into or out of a trust. The new assessed value is based on the sale price or fair market value at the time of transfer.

California law exempts certain transfers from reassessment: transfers between spouses, transfers to children under Proposition 58 (if the property value does not exceed $1 million, or $2 million in some counties), and transfers to parents under Proposition 193. These exemptions preserve the low assessed value across generations, though you must file a claim with the assessor within three years of the transfer.

New construction or major improvements also trigger reassessment of the added value. The assessor inspects completed work and adjusts your assessment upward. Minor repairs and maintenance do not trigger reassessment.

When reassessment occurs, you receive a supplemental bill for the remainder of the fiscal year (July through June in California). This bill covers the tax on the new assessed value from the date of change through June 30. The following fiscal year, your regular bill reflects the new value for the full year.

Reading your assessment notice and filing an appeal

Each fall, the assessor mails a Notice of Assessed Value showing the assessed value for the coming fiscal year. This notice includes the property address, a brief description, the assessed land value and building value separately, and the total. It also shows the prior year's value so you can see the change.

If you believe the assessed value is wrong, you have 30 days from the mailing date to file a written appeal with the assessor. You do not need a lawyer or professional to file. Write a letter explaining why you think the value is too high, include supporting evidence (recent appraisal, comparable sales, photos of damage or needed repairs), and mail it to the assessor's office. Keep a copy for your records.

The assessor will review your appeal and either adjust the value, deny it, or offer a compromise. If you disagree with the result, you can appeal to the county Assessment Appeals Board, a separate body that hears disputes. This second appeal also has a important date, usually 60 days after the assessor's decision. The Appeals Board is free to use; many people represent themselves.

If you miss the 30-day window to appeal the assessor's notice, you may still challenge the value through a Proposition 8 process, which is available year-round but requires showing that the property value has declined due to damage, economic obsolescence, or other factors. This route is slower and has a higher burden of proof.

Local assessments and bonds on your bill

Your property tax bill includes the 1% base rate plus any voter-approved assessments specific to your area. These are separate from the base rate and appear as line items on your bill. Common examples include school bonds, fire district assessments, water district charges, and community facility districts.

These assessments are approved by local voters and vary by location. A property in one school district may pay a different assessment than an identical property across the street in a different district. The assessor's office can tell you which assessments explore to your address.

Some assessments are based on assessed value (like the 1% base rate), while others are a flat fee per parcel or based on square footage or other factors. Your tax bill itemizes each one so you can see what you are paying for.

Frequently Asked Questions

How do I find out what my property is assessed at?

Contact your county assessor's office or visit their website. Most counties now post assessment data online by address or parcel number. You can also call the assessor's office and ask for the assessed value. The information is public record.

Can I lower my property tax by lowering my assessed value?

Only if the assessed value is genuinely wrong. You cannot lower it by claiming the property is worth less than the assessor determined unless you have evidence: a recent appraisal, comparable sales data, or documentation of damage or needed repairs. The assessor will review your evidence and adjust if warranted.

What happens to my property tax if I make major renovations?

The assessor may increase your assessed value to reflect the improvements. The increase applies only to the added value from the renovation, not your entire property. You can appeal the new value if you believe it is too high.

Do I pay property tax on the market value or the assessed value?

You pay tax on the assessed value, which may be much lower than market value due to Proposition 13. The assessed value is what appears on your tax bill, not the price your home would sell for today.

What if I inherit property from a parent?

Under Proposition 58, you may transfer the property without reassessment if the property value does not exceed $1 million (or $2 million in some counties). You must file a claim with the assessor within three years of the transfer to preserve the low assessed value. Without the claim, the property is reassessed at market value.