California property tax starts with the county assessor's valuation, not your purchase price

California property tax is calculated by multiplying your property's assessed value by the local tax rate. The county assessor determines the assessed value, and your county and local districts set the tax rate. The formula is straightforward: Assessed Value × Tax Rate = Annual Property Tax. What makes California different from most states is Proposition 13, passed in 1978, which caps how much your assessed value can increase each year and limits the base tax rate to 1 percent.

The assessed value is not what you paid for the property or what it would sell for today. Instead, the assessor sets an initial value based on the property's market value at the time of purchase or transfer. After that, the value can only increase by up to 2 percent per year, regardless of how much the property's actual market value rises. This means two identical houses on the same street can have very different assessed values if one was purchased decades ago and the other recently.

Key Takeaways

  • Your assessed value is set by the county assessor based on your property's market value when you bought it or when ownership transferred, then increases by no more than 2 percent annually under Proposition 13.
  • The base tax rate in California is 1 percent of assessed value, but your total rate is usually higher because of voter-approved bonds and special district taxes added on top.
  • You can request a reassessment if you believe the assessor's value is wrong, and you have the right to see the assessor's records and comparable sales data they used.
  • Property tax bills arrive in two installments per year, typically in November and February, and are due by specific dates or penalties apply.
  • New construction, property transfers, and certain changes to the property trigger a reassessment, which can significantly raise your tax bill.

How the county assessor determines your property's assessed value

The county assessor's office is responsible for valuing every property in the county. For most residential properties, they use the market data approach: they look at recent sales of comparable properties in your area and adjust for differences in size, condition, location, and features. If your house sold recently, they may use that sale price as the starting point. If it has been years since you bought, they estimate current market value based on similar homes that have sold recently.

The assessor does not visit every property every year. Instead, they use public records, county records of sales, and periodic field inspections to maintain their valuation. You can request a copy of the assessor's record for your property, which shows the assessed value, the land value, the improvement value, and the data they used to calculate it. This record is public and available at the county assessor's office or online through most county websites.

Once the assessor sets an initial value, Proposition 13 limits increases. Your assessed value can go up by no more than 2 percent per year, even if your home's market value doubles. The only exception is when the property transfers to a new owner or when you make major improvements. A transfer resets the assessed value to current market value, which is why property tax bills often jump sharply after a sale.

Understanding the tax rate: base rate plus voter-approved additions

The base property tax rate in California is 1 percent of assessed value. However, your actual rate is almost always higher because of additional taxes voters have approved. These additions come from school districts, county services, city services, water districts, fire districts, and other local agencies. Each of these can ask voters to approve a bond measure or tax increase, and if approved, that amount is added to your bill.

Your total tax rate varies by location. A property in one city might have a total rate of 1.2 percent, while an identical property in a neighboring city might be 1.35 percent, depending on which bonds and special taxes apply. You can find your specific rate by looking at your property tax bill or by contacting your county assessor's office. The bill itself breaks down the 1 percent base rate and each additional tax separately, so you can see exactly where your money goes.

Voter-approved bonds are common and usually fund schools, libraries, parks, or infrastructure. These are temporary taxes that expire after a set number of years. Permanent tax increases are less common and require a higher voter threshold. When you see a property tax bill that seems high compared to a neighbor's, the difference is usually in these additional local taxes, not in the base rate or assessed value.

The step-by-step calculation with a real example

Here is how the calculation works in practice. Suppose you bought a house in Sacramento County for $400,000. The assessor sets your initial assessed value at $400,000. Your county's base rate is 1 percent, and your local school district has a voter-approved tax of 0.35 percent. Your total tax rate is 1.35 percent.

Year 1 tax bill: $400,000 × 0.0135 = $5,400 per year, or $2,700 per installment.

In Year 2, your assessed value increases by 2 percent (the maximum allowed): $400,000 × 1.02 = $408,000. Your new tax bill is $408,000 × 0.0135 = $5,508 per year.

Now suppose the house sells to a new owner for $550,000. The assessor resets the assessed value to $550,000, and the new owner's first tax bill jumps to $550,000 × 0.0135 = $7,425 per year. This is why property tax bills often increase significantly after a sale, even though the base rate and tax rate have not changed.

When your property gets reassessed and your tax bill changes

Your assessed value is not locked in forever. It increases by up to 2 percent annually, but it also resets when certain events happen. A change in ownership is the most common trigger. When you sell the property or transfer it to someone else, the assessor reassesses it at current market value. This can cause a large jump in your tax bill if the property has appreciated significantly since the last assessment.

New construction or major improvements also trigger reassessment. If you add a room, finish a basement, or build a pool, the assessor will increase the assessed value to reflect the improvement. Minor repairs and maintenance do not trigger reassessment. The line between improvement and repair is sometimes unclear, and disputes over this are common. Generally, if the work adds value to the property or extends its useful life, it is an improvement.

Some transfers do not trigger reassessment. If you transfer property to a spouse, child, or grandchild, or if a property passes through a trust to a family member, the assessed value may not reset, depending on the specific circumstances and whether certain conditions are met. These rules are complex, and if you are planning a transfer, it is worth asking the assessor's office about the reassessment consequences before you proceed.

How to challenge your assessed value if you think it is wrong

If you believe the assessor's valuation is incorrect, you have the right to file a Proposition 8 assessment appeal. This is a formal process, but it does not require a lawyer. You must file within 30 days of receiving your property tax bill, or you lose the right to appeal that year. The deadline is strict, so mark your calendar when your bill arrives.

To file an appeal, you submit a form to the county assessor's office stating why you think the value is wrong. You can argue that comparable sales data is outdated, that the assessor made an error in measuring the property, or that the property has a defect that reduces its value. You will need to provide evidence: recent appraisals, comparable sales in your area, photographs of damage or defects, or expert opinions.

If the assessor does not agree with your appeal, you can request a hearing before the county Assessment Appeals Board. This is a separate body that reviews disputes between property owners and the assessor. The hearing is informal, and you can present your evidence and argue your case. If you win, the assessed value is reduced, and your tax bill goes down retroactively to the year you filed. If you lose, you can appeal to the county Superior Court, though this is expensive and rarely pursued.

Reading your property tax bill and understanding what you owe

California property tax bills are sent twice per year, usually in November and February. The bill shows your assessed value, your tax rate, the total tax owed, and the due date. It also breaks down the 1 percent base rate and each additional tax separately, so you can see how much goes to schools, county services, and other agencies.

The bill lists two installments: the first is due by December 10, and the second is due by April 10. If you pay late, a 10 percent penalty is added immediately. If you pay more than one month late, an additional 1.5 percent penalty accrues monthly. These penalties add up quickly, so paying on time is important. If you cannot pay in full, you can contact the county tax collector about a payment plan.

Some property owners set up automatic payments through their bank or the county tax collector's office. Others pay online through the county website. The bill itself includes instructions for payment and the mailing address if you pay by check. If you do not receive a bill, contact the county tax collector immediately, because nonpayment can lead to a tax sale of the property after several years of delinquency.

Frequently Asked Questions

Does my property tax go up every year?

Yes, but only by up to 2 percent annually under Proposition 13. If your assessed value is $400,000, it can increase to $408,000 the next year, then $416,160 the year after that. The only exception is if your property transfers to a new owner, in which case it resets to current market value and may jump significantly.

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

Yes, if you can show the assessor's value is wrong. You must file a Proposition 8 appeal within 30 days of receiving your bill. You will need evidence like recent appraisals, comparable sales, or documentation of property defects. If you win, your assessed value is reduced and your tax bill goes down.

What happens if I do not pay my property tax bill on time?

A 10 percent penalty is added immediately if you miss the due date. An additional 1.5 percent penalty accrues each month after that. If taxes remain unpaid for several years, the county can sell the property at a tax sale to recover the debt.

Does adding a room or finishing a basement increase my property tax?

Yes. Major improvements trigger a reassessment, and the assessor will increase the assessed value to reflect the added value. Minor repairs and maintenance do not trigger reassessment. If you are unsure whether your project counts as an improvement, ask the assessor's office before you start work.

Why did my property tax bill jump after I bought the house?

When you purchased the property, the assessor reset the assessed value to your purchase price. If the previous owner bought it years ago, their assessed value was much lower due to the 2 percent annual cap. Your bill jumped because the assessed value increased to current market value, not because the tax rate changed.