California property tax starts with the county assessor's valuation, not what you paid

Your property tax bill in California comes from a formula: the county assessor sets a value for your property, then multiplies that value by the tax rate (called the millage rate) set by your county and local districts. The assessor's valuation is the piece most people misunderstand. It is not based on what similar homes sold for last month. Instead, it is based on Proposition 13, a 1978 state law that caps how much the assessed value can rise each year.

Here is how it works in practice: when you buy a house, the assessor sets the assessed value at or near your purchase price. Each year after that, the assessed value can increase by no more than 2 percent, regardless of whether your home's market value doubled. The only time the assessed value resets to current market value is when the property changes ownership. This means two identical houses on the same street can have very different assessed values — and therefore very different tax bills — depending on when each owner bought.

Once the assessor sets the value, the county multiplies it by the tax rate. In California, the base rate is 1 percent of assessed value, but your actual rate is usually higher because county, city, school district, and special district taxes are stacked on top. The total rate varies by location and can range from about 0.76 percent to over 1.25 percent of assessed value.

Key Takeaways

  • The county assessor determines your property's assessed value, which is capped at a 2 percent annual increase under Proposition 13 unless the property is sold.
  • Your tax bill equals the assessed value multiplied by the combined tax rate (base 1 percent plus local district taxes), which varies by county and city.
  • You can find your assessed value and tax rate on your property tax bill or by searching the county assessor's website using your address or parcel number.
  • If you believe the assessor's valuation is wrong, you can file a Proposition 8 appeal with the county assessor's office, usually within 30 days of receiving your bill.

Where to find your assessed value and current tax rate

Your property tax bill, mailed by the county tax collector, shows both the assessed value and the tax rate used to calculate what you owe. The bill arrives in two installments per year (usually November and February). If you have lost your bill or need to check the value before the bill arrives, you can search the county assessor's website directly.

Each county assessor maintains a public database, usually searchable by address or parcel number. Search "[your county name] assessor" plus "property search" or "assessment roll" to find the database. The assessor's site will show you the current assessed value, the land value and improvement value separately, and sometimes the prior year's value so you can see the 2 percent increase. Some counties also show the tax rate breakdown by district.

If you cannot find the information online, you can visit the county assessor's office in person or call. Bring your address or parcel number (found on your property tax bill or deed). The assessor's office is required to provide this information at no cost.

How the 2 percent annual increase works under Proposition 13

Each year, the assessor automatically increases your assessed value by up to 2 percent. The increase is not discretionary — it happens unless you file an appeal. The 2 percent is applied to the prior year's assessed value, so the increases compound slightly over time, but the growth is still much slower than market appreciation in most California neighborhoods.

The only exception is a change in ownership. When a property is sold, the assessor resets the assessed value to the sale price (or fair market value if the sale price is below market). This is why a new owner often pays significantly more in property tax than the previous owner, even though the houses are identical. After the ownership change, the 2 percent annual increase starts over from the new, higher base.

Some transfers do not trigger a reassessment. If you inherit the property or receive it as a gift from a parent or grandparent, Proposition 19 (passed in 2020) allows a limited reassessment exemption for the primary residence, though the rules are complex and depend on the relationship and the property type. Consult a tax professional or the assessor's office if you are in this situation.

The tax rate: base rate plus local district taxes

California's base property tax rate is 1 percent of assessed value, set by state law. However, your actual rate is higher because counties, cities, school districts, and special districts (such as water or fire districts) each add their own tax on top. These are called voter-approved bonds or special assessments, and they vary widely by location.

For example, one county might have a combined rate of 1.15 percent, while a neighboring county has 1.08 percent. Within a single county, a city with a strong school district and active special districts might have a rate of 1.25 percent, while a rural area has 0.95 percent. Your tax bill shows the breakdown by district so you can see which agencies are taxing the property.

The tax rate does not change based on your income, age, or personal circumstances. It is the same for every property in the same taxing district, regardless of who owns it. However, some property owners may be exempt from property tax entirely (such as nonprofits, religious organizations, or government agencies), but that is a separate matter from the rate calculation.

What happens if you think the assessed value is wrong

If you believe the county assessor has overvalued your property, you can file a Proposition 8 appeal (also called a value reduction appeal). This is different from a Proposition 13 appeal and is based on the argument that the assessed value exceeds the property's fair market value. You typically have 30 days from the date you receive your property tax bill to file.

To file, contact the county assessor's office and request a Proposition 8 appeal form. You will need to provide evidence that the property is worth less than the assessed value — usually comparable sales of similar properties in the area, an appraisal, or documentation of physical damage or defects. The assessor will review your evidence and either reduce the value or deny the appeal. If denied, you can appeal to the county Assessment Appeals Board, which is an independent body.

The deadline to file is strict, so mark your calendar when you receive your bill. If you miss the deadline, you cannot appeal that year's value, but you can appeal the following year's value if it increases again. Some counties allow online filing, while others require a paper form submitted in person or by mail.

How new construction and improvements affect your assessed value

When you add a new building, major renovation, or significant improvement to your property, the assessor may increase the assessed value beyond the normal 2 percent. The assessor's office monitors building permits and property records to identify improvements. Once an improvement is discovered, the assessed value is adjusted upward to reflect the added value.

The increase is not retroactive to the date the work was completed. Instead, the new assessed value typically takes effect on the next assessment roll, which is usually January 1 of the following year. So if you finish a major renovation in March, the increased value usually appears on your bill for the fiscal year beginning July 1 of that year (or January 1, depending on your county's billing cycle).

Minor repairs and maintenance do not trigger a reassessment. The distinction is whether the work adds value to the property or merely maintains it. A new roof or fresh paint is maintenance. An addition, a new deck, or a pool is an improvement. If you are unsure, ask the assessor's office before starting work.

Frequently Asked Questions

Can I lower my property tax by reducing the assessed value?

Yes, through a Proposition 8 appeal if you can show the assessed value exceeds fair market value. You need evidence such as comparable sales, an appraisal, or documentation of defects. The appeal must be filed within 30 days of receiving your tax bill. If the assessor denies it, you can appeal to the county Assessment Appeals Board.

Why is my neighbor's tax bill so much lower than mine if our houses are the same?

Likely because your neighbor bought their house earlier and has benefited from Proposition 13's 2 percent annual cap, while you bought more recently at a higher price. When a property sells, the assessed value resets to the sale price. After that, it only increases 2 percent per year, so long-time owners pay much less than new owners on identical properties.

Does my property tax go up automatically every year?

Yes. The assessed value increases by up to 2 percent each year automatically under Proposition 13, unless you file an appeal. The tax rate (the percentage applied to the assessed value) can also change if your county or local districts pass new bonds or special assessments, though this is less common.

What is the difference between Proposition 8 and Proposition 13 appeals?

Proposition 13 appeals challenge whether the assessor correctly applied the 2 percent increase formula. Proposition 8 appeals argue the assessed value is too high compared to fair market value. Most homeowners file Proposition 8 appeals. Both must be filed within 30 days of receiving your tax bill.

If I make major improvements to my house, will my property tax increase?

Yes. Improvements like additions, new pools, or major renovations trigger a reassessment and increase the assessed value. The assessor monitors building permits to identify improvements. The new value usually takes effect on the next assessment roll (January 1 in most counties), not retroactively to when the work was done.