Property tax starts with two numbers: what your assessor says your property is worth, and the tax rate your local government sets

Property tax is not a percentage of what you paid for your home or what you could sell it for today. Instead, your tax bill comes from multiplying two separate figures: the assessed value (what your local assessor estimates your property is worth) and the tax rate (the percentage your city, county, or school district charges). The assessor's job is to estimate value. The tax rate is set by elected officials or determined by state law. You pay tax on the assessed value, not the market value, and these two numbers are often very different.

The formula is straightforward once you have both numbers: assessed value × tax rate = your annual tax bill. But getting to those two numbers involves different people, different methods, and different rules depending on where you live. Understanding how each piece works helps you read your tax bill and know when you might challenge it.

Key Takeaways

  • Your property tax bill equals the assessed value times the tax rate, and the assessed value is usually lower than what your home would sell for.
  • Assessors estimate value using sales of similar homes, income from rental properties, or the cost to rebuild your home, depending on the property type.
  • Tax rates vary by location and are set by your county, city, school district, and other local bodies — not by a single formula.
  • Some states cap how much the assessed value can increase each year, even if your home's market value rises sharply.
  • You can challenge your assessed value if you believe it is too high, usually through a formal appeal process in your county.

How assessors estimate the value of your home

Assessors use three main methods to estimate what your property is worth. The most common is the sales comparison approach: the assessor looks at recent sales of homes similar to yours in your area — same size, age, condition, and location — and adjusts for differences. If your home has a pool and the comparable home does not, the assessor might add a value for that feature. If your home needs a new roof and the comparable does not, the assessor might subtract.

For rental properties and apartments, assessors often use the income approach. They estimate how much rent the property generates each year, subtract operating costs, and calculate what an investor would pay for that income stream. A four-unit apartment building is valued differently than a single-family home because the income it produces is the main driver of its worth.

The third method is the cost approach, used mainly for newer homes or properties with few recent sales nearby. The assessor estimates what it would cost to rebuild your home from scratch, adds the land value, and subtracts depreciation for age and wear. This method is less common because it does not account for market demand the way sales comparison does. Most assessors use a combination of these methods and weight them differently depending on the property type and available data.

What the tax rate is and who sets it

The tax rate is expressed as a percentage or as a dollar amount per $1,000 of assessed value. For example, a rate might be 1.2% of assessed value, or $12 per $1,000 of assessed value — these mean the same thing. The tax rate is not set by a single body. Instead, multiple local governments — your county, city, school district, and sometimes special districts for fire, water, or libraries — each set their own rate, and your total tax bill is the sum of all of them.

In most states, the county assessor's office estimates value, but the county commission, city council, or school board votes on the tax rate. Some states set a statewide cap on rates. Others allow local voters to approve rate increases through ballot measures. A few states use a formula based on the previous year's rate and population growth. The process varies significantly by state, so the rate in your county may work very differently from the rate in a neighbouring county. Your tax bill lists each rate separately so you can see which government body is charging you what.

How assessed value and market value differ

Your home's assessed value is what the assessor estimates it is worth for tax purposes. Your home's market value is what a buyer would actually pay for it today. These are often different, sometimes by a lot. In a hot real estate market, homes sell for well above assessed value. In a declining market, assessed value can be higher than market value.

Many states use assessment ratios to keep assessed value lower than market value on purpose. An assessment ratio of 50% means the assessed value is supposed to be half the market value. A ratio of 100% means they should be equal. The ratio is set by state law and varies by property type — residential, commercial, agricultural, and industrial property often have different ratios. Even with a ratio in place, the actual assessed value may not match it perfectly because assessors work with incomplete information and estimates. Your county assessor's office can tell you what ratio applies to your property.

Caps on how much assessed value can increase

Some states limit how much the assessed value can go up each year, even if your home's market value rises. Proposition 13 in California, for example, caps increases at 2% per year unless the property is sold. This means a home bought in 1990 might have a much lower assessed value than an identical home bought last year on the same street. Other states like Florida and Texas have homestead exemptions that freeze assessed value for primary residences under certain conditions.

These caps protect long-term homeowners from sudden tax spikes when their neighbourhood becomes more desirable. However, they also mean that newer residents pay more tax than older residents for similar homes, and they can reduce revenue for schools and local services. Not all states have caps. Some reassess property value every year with no limit on increases. Check your state's rules to understand whether your assessed value is protected from large jumps. Your county assessor can explain what limits, if any, explore where you live.

The formula: assessed value times tax rate

Once you know the assessed value and the tax rate, the calculation is straightforward. If your home's assessed value is $300,000 and your total tax rate is 1.2%, your annual tax bill is $300,000 × 0.012 = $3,600. If the rate is expressed as $12 per $1,000, divide your assessed value by 1,000 and multiply: ($300,000 ÷ 1,000) × $12 = $3,600. Both methods give the same answer.

Your actual bill may include additional charges. If you have a mortgage, your lender may require you to pay property tax through an escrow account as part of your monthly payment. If you are behind on taxes, penalties and interest are added. If your property is in a special district — a fire protection district or water management district — that district's rate is added to your bill. The base calculation is always assessed value times rate, but the final bill you receive may be higher. Your tax bill should break down each component so you can see what you are paying for.

How to find your assessed value and tax rate

Your assessed value and tax rate are public record. You can find them on your property tax bill, which your county assessor or tax collector mails to you each year. The bill usually shows the assessed value, the tax rate (or rates, if multiple districts tax your property), and the total tax due. You can also search online through your county assessor's website — most counties have a searchable database where you enter your address or parcel number and see the assessed value.

If you cannot find your information online, call your county assessor's office directly. They can tell you the assessed value, explain which tax rates explore to your property, and answer questions about how the value was estimated. If you believe the assessed value is wrong, the assessor's office can also explain how to file a formal challenge, which usually must be done within a specific time window after the assessment is mailed. Many counties also hold open houses or information sessions before the appeal important date.

Frequently Asked Questions

Why is my assessed value so different from what I paid for my house?

Assessed value and purchase price are calculated differently. The assessor estimates current market value using comparable sales, not your purchase price. If you bought your home years ago, the market may have changed. If you bought recently but paid more than similar homes sold for, the assessor may value it lower. If you bought in a down market and prices have risen, the assessed value may be higher than what you paid.

Can I lower my assessed value?

Yes, you can challenge your assessed value through a formal appeal process in your county. You typically file a written objection within a set time frame (often 30 to 45 days after the assessment is mailed) and provide evidence that the value is too high — comparable sales of lower-priced homes, a recent appraisal, or documentation of property damage. The process and important date vary by state and county, so contact your assessor's office for the specific steps in your area.

Does the tax rate ever change?

Yes. Tax rates are set by local governments and can change year to year based on budget needs and state law. Some states allow rates to increase only by a certain percentage annually. Others require voter approval for rate increases. A few states have rate caps. Your tax bill can go up even if your assessed value stays the same, because the rate went up. Check your county's budget process or website to see if rate changes are planned.

What happens if I disagree with the assessed value but miss the appeal important date?

Missing the important date usually means you cannot challenge that year's assessment. However, you can typically appeal the next year's assessment when it is issued. Some counties allow late appeals in hardship cases, so contact your assessor's office to ask if an exception is possible. Keep records of why you believe the value is wrong so you can file promptly next time.

How often does the assessor re-evaluate my property?

The frequency varies by state and county. Some areas reassess every year. Others reassess every three to five years. A few reassess only when the property is sold. Check your county assessor's website or call to find out the schedule for your area. Even if a full reassessment is not done, you can still file an appeal if you believe the current value is incorrect.