How to determine property tax: a step-by-step guide

Last updated 2026-07-09

What is the basic formula for calculating property tax?

Property tax = (Assessed Value minus Exemptions) x Tax Rate. That's the whole thing. Every complication you'll run into is a variation on one of those three numbers.

Assessed value is what the county assessor says your property is worth for tax purposes. The tax rate, often called the mill rate or millage rate, is set by your local taxing districts. Exemptions cut the taxable portion of your value before the rate hits it.

Here's a concrete example. Your home carries an assessed value of $300,000. You qualify for a $50,000 homestead exemption. Your combined mill rate is 20 mills, which equals 2%. Taxable value is $250,000. Multiply by 0.02 and you owe $5,000 in annual property taxes.

One mill equals $1 of tax per $1,000 of taxable value ^[1]. So 20 mills on $250,000 works out to 20 x $250 = $5,000. Same answer, two roads. Use whichever form your county's website prints the rate in.

How does assessed value get determined?

This is where most property tax trouble starts. Your assessor doesn't appraise your home every year the way a mortgage lender does. Most counties run mass appraisal models that estimate market value from recent sales of comparable properties, then apply an assessment ratio to reach assessed value ^[2].

Assessment ratios change by state and sometimes by property class. In California, under Proposition 13, assessed value is generally capped at the 1975-76 base value plus a maximum 2% annual increase until the property sells ^[3]. In Cook County, Illinois, residential property is assessed at 10% of market value. In Texas, assessed value is supposed to equal 100% of market value but caps at 10% annual increases for homesteaded properties ^[4]. In New York State, individual localities set their own assessment ratios, which is why the phrase "equalization rate" comes up in any New York appeal.

Here's the practical move. Find your county assessor's website and pull up your property record. It shows the market value estimate, the assessment ratio, and the assessed value that comes out the other end. If the market value estimate is higher than what you could actually sell your home for today, you have grounds to appeal. That one number drives everything below it.

Mass appraisal models get things wrong at a real rate. The IAAO (International Association of Assessing Officers) sets a standard that a jurisdiction's median assessment ratio should land between 90% and 110% of the legal target, with a coefficient of dispersion under 15% for residential property ^[2]. Plenty of jurisdictions miss those bounds, which means some owners pay more than their share year after year.

What is a mill rate and how do you find yours?

A mill rate is a tax rate stated in thousandths. One mill equals $1 per $1,000 of taxable value. Your bill stacks mill rates from several taxing districts on top of each other: the county, the municipality or township, the school district, and sometimes special districts for fire protection or a community college. You can't opt out of any of them.

Find your rate on your tax bill or your county assessor's or treasurer's website. The bill usually breaks out each district. Add them for your total.

If your county shows rates as a percentage instead of mills, the math is quick. A 1.5% rate equals 15 mills. A 0.8% rate equals 8 mills.

The national median effective property tax rate on owner-occupied housing was about 1.10% in 2022, per the Tax Foundation's analysis of U.S. Census Bureau data ^[5]. That median hides a huge spread. New Jersey topped the list around 2.23%. Hawaii sat near the floor at 0.32%. Your local rate could run well above or below the middle.

For metro-level math, la county property tax, nyc property tax, and miami dade property taxes each carry their own rate structures worth a look if you live there.

How do exemptions reduce your property tax bill?

Exemptions cut taxable value before the mill rate applies, so the dollars they save you scale with your local rate. A $25,000 homestead exemption in a 2% jurisdiction saves $500 a year. The same exemption in a 1% jurisdiction saves $250.

The common ones:

• Homestead exemption: lowers taxable value on a primary residence. Texas offers a mandatory $100,000 school district homestead exemption starting in 2023 ^[4].
• Senior citizen exemption: available in most states above a set age, often 65.
• Disability exemption: rules run all over the map. Some states freeze assessed value, others knock off a flat amount.
• Veteran and surviving spouse exemptions: also common, amount depends on state law.
• Agricultural use exemptions: land in active farming may be assessed at use value instead of market value.

Exemptions aren't automatic in most places. You apply, sometimes once, sometimes every year. If you've owned your home for years and never filed for a homestead exemption, you're probably overpaying right now, and depending on your state you can often claw back a few years.

Search "[your county] assessor exemption application" for the form. Most run one page and want proof of residency.

For counties with detailed exemption rules, santa clara property tax and contra costa county property tax both cover California exemptions in depth.

Step-by-step: how to calculate your own property tax

Here's the process end to end. Do the steps in order.

Step 1: Find your assessed value. Go to your county assessor's website and search by address. Your record shows market value (their estimate) and assessed value (market value x assessment ratio). Write down the assessed value.

Step 2: Find and apply your exemptions. Check the same record or your tax bill for exemptions already on file. If you qualify for one that isn't showing, apply before you move on.

Step 3: Calculate taxable value. Taxable value = assessed value minus exemptions. If your county prints a separate "taxable value" field, use that number straight.

Step 4: Find your total mill rate. Pull last year's tax bill. It usually lists each district with its own rate. Add them up. Convert to a decimal (divide by 1,000 for mills, or by 100 for a percent).

Step 5: Multiply. Taxable value x decimal rate = annual property tax.

Step 6: Check against your actual bill. If your number and the bill don't match within a few dollars, something needs explaining. The usual culprit is special assessments (road paving, sewers, and the like) that get added separately and aren't tied to mill rates.

Special assessments trip people up constantly. They land on your tax bill, but they're charged per parcel or per front foot, not as a percentage of value, so they never show up in the formula above. Read your bill line by line.

For Texas math, collin county property tax and williamson county property tax walk through the Texas Notice of Appraised Value and the protest process.

How do you check if your assessed value is too high?

Start with comparable sales. Your assessor set a value with a model, and models miss. You can test it the same way the model built it: find what similar homes near you actually sold for in the 6 to 12 months before your assessment date.

Most county assessor sites let you search by neighborhood and filter by sale date. Match on square footage, age, condition, bed and bath count, and lot size. Three to five solid comps is enough. If the average sale price of those homes sits well below what your assessor claims yours is worth, that gap is your appeal.

Material means something specific. A $5,000 difference on a $400,000 assessment isn't worth your Saturday. A $40,000 difference almost always is.

Beyond comps, hunt for errors in your property record. Assessors carry wrong data all the time: the wrong bathroom count, a finished basement logged as unfinished, square footage pulled from a permit for work that never got built. Factual errors are easier to win than pure valuation fights, because you don't need a full market analysis, just proof (a photo, a floor plan, a prior appraisal).

The Lincoln Institute of Land Policy has documented that lower-value homes in many jurisdictions get assessed at higher effective rates relative to market value than higher-value homes, a pattern called regressive assessment ^[6]. If you own a modest home, the odds your assessment runs proportionally higher than your wealthier neighbors' assessments are above average.

Once you've confirmed an overassessment, a DIY appeal kit (like the one at TaxFightBack) hands you the forms, comp worksheets, and filing instructions to make the argument yourself instead of surrendering a 30 to 40% contingency fee to a tax agent.

What drives your property tax bill up year to year?

Three things push your bill higher: a higher assessed value, a higher mill rate, or a lost exemption.

Assessed value climbs when the market rises and your assessor's model tracks it, or when you pull a permit for an addition or renovation. In states without assessment caps, a hot market can spike bills in a single reassessment cycle. In California, assessed value can only rise from a sale or new construction. General market appreciation doesn't trigger a reassessment under Prop 13 ^[3].

Mill rates rise when local governments need more revenue and the tax base isn't growing fast enough to cover it. School district levies are the single biggest driver of mill rate increases in most places, and voters often set them by referendum.

A lost exemption can spike your bill with no change in value at all. It happens when a senior exemption lapses on a missed annual renewal, or when a property changes hands and the homestead exemption doesn't carry over to the new owner.

When your bill jumps, figure out which of the three caused it before you decide to appeal. If the mill rate went up but your assessed value is accurate, appealing the assessment does nothing. Your fight is at the local budget table instead.

For a wider view of how property tax systems are built, see property tax taxation.

How do different states handle property tax differently?

There is no national property tax system. Each state writes its own rules, and inside each state, counties and municipalities pile on their own. The variation is genuinely large.

State	Avg. Effective Rate (2022)	Assessment Ratio	Reassessment Cycle
New Jersey	~2.23%	100% of market	Annual
Illinois	~2.05%	Varies by county (10% in Cook County)	3-4 years
Texas	~1.60%	100% of market, 10% cap for homestead	Annual
California	~0.76%	1% base rate; value capped at 2%/yr increase	Sale/new construction triggers
Florida	~0.89%	100% of just value; Save Our Homes cap 3%/yr	Annual
Hawaii	~0.32%	100% of market	Annual

Sources: Tax Foundation ^[5], Lincoln Institute of Land Policy ^[6], California State Board of Equalization ^[3], Texas Comptroller ^[4].

States also split on appeal deadlines (some as short as 30 days after the notice, others 90 days or more), who hears the appeal (an informal review board, a formal administrative tribunal, or a direct court filing), and what evidence they'll accept.

In a high-rate state like New Jersey or Illinois, a win pays off bigger in raw dollars. Cut the assessed value on a $400,000 New Jersey home by 10% and you save roughly $890 a year at the 2.23% average rate. The same cut in Hawaii saves about $128.

For Minnesota rates and assessment rules, hennepin county property tax covers that market. Michigan's odd setup runs in detroit property taxes.

When should you appeal your property tax assessment?

Appeal when your evidence shows the assessed value tops what your home would realistically sell for, or when your property record holds a factual error. Those are the two winning cases.

Don't appeal just because the bill went up. If comparable homes back the assessor's value, you lose on value grounds. And don't wait for someone to fix it for you. Nobody will.

Deadlines are firm almost everywhere. Miss it and you wait for next year. They usually run 30 to 90 days after the assessment notice is mailed, which in most places lands in spring. Some jurisdictions stack an informal protest stage and a later formal hearing stage, each with its own clock.

Check your notice the day it lands in the mailbox. The deadline is usually printed right on it. If no notice showed up, look up your property on the assessor's website. The assessment date is public.

The National Taxpayers Union Foundation estimates that only about 5% of homeowners who could win an appeal actually file one ^[7]. The barrier is information, not legal difficulty. The process is administrative, not a courtroom. At the first informal level you show your comps and ask for a review.

If you want to run the whole thing yourself, TaxFightBack's appeal kit includes state-specific deadline calendars and evidence templates so the window doesn't slip past you.

How can you pay your property tax and what happens if you don't?

Most counties take payment online, by mail, or in person. Many offer installments: two payments a year is common, four in some places. Some charge a small convenience fee on credit cards.

For payment portals in your area, online tax payment for property covers how county systems work.

Miss a deadline and the consequences climb in stages. First come late fees and interest (typically 1 to 2% per month). Let it run long enough and the county places a tax lien on the property. A lien is a public record and blocks a sale or refinance. Leave the lien unpaid and the county can eventually pursue tax deed foreclosure and take the title.

The timeline from first missed payment to foreclosure changes by state. Illinois gives a two-year redemption period after a tax sale before the buyer can apply for a deed ^[8]. Other states move faster.

If you're genuinely struggling to pay, most counties run hardship deferral or payment plan programs, and many states offer circuit breaker programs that cap property tax as a share of income for low-income households. The National Conference of State Legislatures tracks these ^[9]. They're underused.

One thing worth knowing. If your mortgage carries an escrow account, your lender pays the tax and collects 1/12 of the estimated annual bill each month. Your lender will never catch or flag an overassessment. That job stays yours.

How do you read a property tax bill?

Property tax bills look intimidating until you know the parts. Here's the structure most of them follow.

Property description: your parcel number (APN or PIN), address, and legal description. The parcel number is what you use to look up your record online.

Assessed and taxable value: sometimes two numbers (assessed minus exemptions = taxable), sometimes just taxable value.

Taxing district breakdown: each district (county, school, city, fire, library) with its rate and its dollar charge. Add these for your total tax before credits.

Exemptions applied: usually shown as deductions in the value section, not the rate section.

Special assessments: line items at the bottom or on a separate notice. These aren't mill-rate taxes. They're flat charges for specific local improvements, and they're generally not appealable through the property tax process.

Due dates: usually two to four per year. Late dates and penalty amounts may sit here too.

If a line looks wrong, the assessor's office will usually explain it over the phone. Call with your parcel number ready. The staff at the counter aren't the enemy. They process thousands of accounts, and errors happen.

For san mateo county property tax bills, the format and supplemental bill timing differ from most other California counties because of the county's reassessment cycle, so bookmark that one if you're in the area.

Frequently asked questions

How do I find my property's assessed value?

Go to your county assessor's website and search by address or parcel number. Your property record is public and shows the market value estimate, the assessment ratio, and the resulting assessed value. If the site is a maze, call the assessor's office with your address and ask for the current assessed value and any exemptions on record. This takes about five minutes.

What is the difference between assessed value and market value?

Market value is what your home would sell for between a willing buyer and seller. Assessed value is the number used to calculate your tax, often a fraction of market value based on your state's assessment ratio. In Texas, assessed value is supposed to equal market value. In Cook County, Illinois, it's 10% of market value. In California, Proposition 13 limits it regardless of current prices.

What is a mill rate and how do I convert it to a percentage?

A mill rate is a tax rate stated per $1,000 of taxable value. To convert to a percentage, divide by 10. A 15-mill rate equals a 1.5% effective rate. To get your bill directly, multiply taxable value by the mill rate, then divide by 1,000. So $200,000 taxable value at 15 mills equals $3,000 a year.

How often can the county reassess my property?

It depends on your state. Many reassess annually. Some run a fixed cycle of two, three, or four years. California only reassesses when ownership transfers or new construction happens. Texas reassesses annually but caps value increases at 10% per year for homesteaded properties. Check your state's rules, because the frequency sets how fast market changes reach your bill.

Can I lower my property tax without appealing the assessment?

Yes. Apply for every exemption you qualify for: homestead, senior, veteran, disability. These cut taxable value immediately with no appeal. Also check your property record for factual errors like wrong square footage or an extra bathroom the assessor invented, and request a correction. Fixing bad data can drop your value without any valuation fight at all.

What happens if my property is over-assessed?

You pay more than your share compared with similarly valued homes. Over-assessment never corrects itself. You have to file an appeal during your jurisdiction's window, typically 30 to 90 days after the notice mails. Present comparable sales that support a lower value and ask the assessor or review board to reduce it. A win cuts your bill for that year and usually carries forward.

Does a higher home sale price automatically raise my neighbor's taxes?

In most states, yes, indirectly. Assessors use recent sales as evidence of market value in their mass appraisal models, so rising neighborhood sale prices tend to push up assessments on unsold homes over time. In California, your neighbor's sale directly affects only their own assessment, not yours, because Proposition 13 pegs each property's value to its own last sale date.

Is property tax deductible on federal income taxes?

Yes, but capped. The Tax Cuts and Jobs Act of 2017 limited the state and local tax (SALT) deduction, which includes property taxes, to $10,000 per year ($5,000 if married filing separately) through at least 2025 ^[10]. If your combined property and income taxes paid to state and local governments top $10,000, you deduct only the first $10,000 on Schedule A.

How do I calculate property tax on a newly purchased home?

In most states, your assessed value resets toward your purchase price at the next reassessment (in California, it resets right at the sale). Multiply your expected new assessed value by the local effective rate to estimate year one. Ask your county assessor's office or escrow officer about the reassessment timeline. Some states take one to two cycles to fully catch up to the new sale price.

What is an equalization rate and why does it matter in New York?

An equalization rate is the ratio of a municipality's assessed value to its full market value, calculated annually by the New York State Office of Real Property Tax Services ^[11]. It matters because towns assess at different percentages of market value. To find implied full value, divide assessed value by the equalization rate. If your town's rate is 80%, a $160,000 assessment implies a $200,000 market value estimate.

How do I appeal my property tax if I think I'm being overcharged?

File a protest or appeal with your local assessor or review board before the deadline printed on your notice. Gather three to five comparable sales of similar homes that closed in the 6 to 12 months before your assessment date. Submit the comps with a short cover letter asking for a reduced value. Most jurisdictions open with an informal review and escalate to a formal hearing if needed. You don't need an attorney for the first stage.

What is a homestead exemption and how much does it save?

A homestead exemption reduces the assessed value taxed on a primary residence. Your savings depend on the local mill rate. Texas offers a $100,000 school district homestead exemption starting in 2023; at a 1% school rate that saves $1,000 a year. Florida's homestead exemption is $25,000 for all levies plus another $25,000 for non-school levies ^[12]. You usually apply once, but check whether your county wants annual renewal.

Can my property tax increase without a reassessment?

Yes. Your bill rises if the mill rate goes up even when assessed value stays flat. School districts and local governments set rates through the annual budget process, and when spending outruns the tax base, rates climb. This is a policy decision, not an assessment error. Your recourse is the local budget hearings and elections, not an appeal.

What is a tax lien and how does it affect my property?

A tax lien is a legal claim the government places on your property for unpaid taxes. It's a public record that surfaces in title searches. You generally can't sell or refinance with an active lien. Leave it unresolved and the county can eventually transfer the property through a tax deed process. Most counties offer payment plans before a lien sale; call the treasurer's office the moment you know you'll miss a payment.

Sources

1. Lincoln Institute of Land Policy, Significant Features of the Property Tax (mill rate definition): One mill equals $1 of tax per $1,000 of taxable assessed value
2. International Association of Assessing Officers (IAAO), Standard on Ratio Studies: IAAO standard requires median assessment ratio between 90% and 110% with coefficient of dispersion below 15% for residential property
3. California State Board of Equalization, Proposition 13 overview: California Prop 13 caps assessed value at the 1975-76 base year value plus maximum 2% annual increase until property sells or new construction occurs
4. Texas Comptroller of Public Accounts, Property Tax Basics: Texas assessed value equals 100% of market value and is capped at 10% annual increase for homesteaded properties; 2023 law increased school district homestead exemption to $100,000
5. Tax Foundation, Property Taxes by State, 2024: National median effective property tax rate on owner-occupied housing was approximately 1.10% in 2022; New Jersey highest at 2.23%, Hawaii lowest at 0.32%
6. Lincoln Institute of Land Policy, Regressivity in Property Assessment research: Lower-value homes in many jurisdictions are assessed at higher effective rates relative to market value than higher-value homes, a pattern known as regressive assessment
7. National Taxpayers Union Foundation, Property Tax Assessment Appeal Study: Approximately 5% of homeowners who could successfully appeal their property tax assessment actually do so
8. Illinois General Assembly, 35 ILCS 200, Property Tax Code: Illinois provides a two-year redemption period after a tax sale before a buyer can apply for a tax deed
9. National Conference of State Legislatures, Property Tax Relief for Homeowners: Circuit breaker programs cap property tax liability as a percentage of income for low-income households; available in most states and underused
10. IRS, Publication 17, Your Federal Income Tax (SALT deduction cap): Tax Cuts and Jobs Act of 2017 capped the state and local tax deduction including property taxes at $10,000 per year ($5,000 married filing separately) through at least 2025
11. New York State Department of Taxation and Finance, Office of Real Property Tax Services, Equalization Rates: New York State calculates annual equalization rates as the ratio of assessed value to full market value for each municipality
12. Florida Department of Revenue, Property Tax Oversight, Homestead Exemption: Florida homestead exemption is $25,000 for all levies plus an additional $25,000 for non-school levies; Save Our Homes caps annual assessment increase at 3%