Property taxes are calculated with a simple formula: take your property’s assessed value, subtract any exemptions you qualify for, and multiply what’s left by the combined local tax rate. The pieces behind that formula — how the assessor sets a value, which exemptions apply, and how each taxing body picks its rate — are where the real variation lives, and they’re what determines the number on your bill.
Step One: Your Property’s Assessed Value
The starting point is the fair market value of your property, which is essentially the price your home would sell for in a normal, arms-length transaction between a willing buyer and a willing seller. Local assessors estimate this using mass appraisal methods that compare recent sales of similar properties in your area to value thousands of parcels at once.
Once the assessor sets a market value, many jurisdictions apply an assessment ratio to arrive at the assessed value. If your home’s market value is $300,000 and your jurisdiction uses a 40 percent assessment ratio, your assessed value becomes $120,000. That ratio is the same for every property within a taxing district. It also differs dramatically from one jurisdiction to the next: some places assess at 100 percent of market value, while others use ratios as low as 10 or 15 percent.
You can check the data behind your assessment by requesting a property record card from your county assessor’s website or office. That card shows the specific details the assessor used: square footage, lot size, year built, number of bedrooms and bathrooms, and recent improvements. Reviewing those details is the fastest way to catch errors that inflate your bill.
Step Two: Subtract Your Exemptions
Before the tax rate is applied, most jurisdictions subtract exemptions from your assessed value to produce a lower taxable value. The most widely available is the homestead exemption, which reduces the taxable value of your primary residence, often by a fixed dollar amount that ranges from a few thousand dollars up to $50,000 or more depending on where you live.
Other common exemptions target specific groups:
- Senior citizens. Many jurisdictions offer additional reductions, freezes, or deferrals for homeowners above a certain age, often 65.
- Veterans and disabled veterans. Exemption size varies, with the largest reductions typically reserved for those with a service-connected disability.
- People with disabilities. Some jurisdictions provide exemptions for homeowners with a qualifying permanent disability regardless of military service.
Exemptions come off the assessed value directly. If your assessed value is $120,000 and you qualify for a $20,000 veteran exemption, your taxable value is $100,000. The market value of your home doesn’t change; only the figure the rate is applied to.
Most exemptions require an application with supporting documentation submitted to your local tax office, and deadlines typically fall early in the calendar year so the exemption applies to the upcoming cycle. Depending on the exemption, you may need proof of age, disability certification, or military discharge papers. Missing the deadline usually means waiting until the following year.
Step Three: Apply the Millage Rate
The tax rate is commonly expressed in mills, where one mill equals one dollar of tax for every $1,000 of taxable value. Multiple local entities set their own millage rate each year: school districts, municipal governments, county governments, and special districts like fire protection or library districts. That’s why your tax statement usually shows several separate line items rather than a single charge.
Each taxing body calculates its rate by dividing its total budget need by the total assessed value of all property in its district. If a school district needs $10 million and the combined assessed value of properties in the district is $1 billion, the school millage rate is 10 mills. Most jurisdictions hold public hearings on the proposed budget and rate before adopting them.
Voter-Approved Levies and Bonds
On top of the base millage, you may see temporary increases that voters approved through a ballot measure. School construction bonds, park improvements, and public safety levies commonly go through a public referendum. If the measure passes (the required margin varies by jurisdiction), a temporary millage is added to your bill for a set number of years until the project is funded or the debt is repaid. These items typically appear as separate line items on your tax statement, so you can see what you’re paying for and when the extra charge expires.
Putting the Formula Together
Once you have your assessed value, your exemptions, and the combined millage rate, the math is straightforward:
- Find your taxable value. Subtract exemptions from the assessed value. A $150,000 assessed value minus a $10,000 senior exemption gives $140,000.
- Convert to taxable units. Divide the taxable value by 1,000. Here, $140,000 ÷ 1,000 = 140.
- Apply the total millage rate. Multiply the units by the combined rate from all taxing bodies. At 50 mills, 140 × 50 = $7,000 in annual property taxes.
Your jurisdiction mails an official tax statement showing the breakdown by taxing entity, the total amount owed, and the due dates. Payment schedules vary. Some areas collect a single annual payment, others split the bill into two semiannual installments, and some use quarterly billing. Check the statement for the exact dates, since schedules differ even between neighboring jurisdictions.
Why the Number Changes From Year to Year
Two of the three inputs move over time. The millage rate is reset annually as each taxing body sets its budget, and your assessed value can shift when the assessor revalues your property.
Reassessment schedules vary widely. Some jurisdictions revalue every property annually. Others operate on cycles of two to five years or longer. Between scheduled reassessments, your assessed value may stay the same or change only by a limited percentage depending on local rules.
Certain events trigger a reassessment outside the normal cycle. The most common are a change of ownership (including sale or inheritance), new construction, major renovations, and the loss of a previously held exemption. Adding a second story or finishing a basement raises market value and will generally show up in a new assessment.
Caps on Annual Assessment Increases
Several states limit how much your assessed value can rise each year on a primary residence, even when actual market value jumps higher. California’s cap restricts annual assessment increases to 2 percent as long as ownership doesn’t change. Florida caps homestead assessment increases at 3 percent per year. Other states use different approaches, including caps applied over a five-year window or gradual phase-ins of large value increases.
These caps can create a growing gap between your assessed value and the current market value of your home. That gap typically resets on sale, since the new owner’s assessment starts from the actual purchase price. If you’ve owned your home for many years in a state with an assessment cap, your taxable value may be significantly lower than what your neighbor paid for an identical house last year.
If You Think the Assessment Is Wrong
If you believe your assessed value is too high, you have the right to challenge it. The process generally moves through two or three stages, starting informally.
Informal Review
Many assessor offices allow you to request an informal review before filing a formal appeal. That can be as simple as calling or visiting the office to point out an error, such as records showing four bedrooms when you only have three or listing more square footage than your home actually has. If the assessor agrees, the value may be adjusted without a formal proceeding. An informal review typically does not preserve your right to appeal further, so check whether you also need to file a formal appeal by the deadline.
Formal Board Hearing
If the informal review doesn’t resolve things, you file a formal appeal with your local board of equalization or review board. Filing deadlines are strict and typically fall within 30 to 90 days of receiving your assessment notice. Administrative fees for filing generally range from about $35 to $300 depending on your jurisdiction and property type.
The burden of proof falls on you. You need credible evidence showing that the assessment exceeds fair market value. The strongest kinds include:
- Comparable sales. Recent sale prices of similar properties in your neighborhood that sold for less than your assessed value.
- Independent appraisal. A professional appraisal conducted within the past year showing a lower value.
- Photos documenting condition issues. Deferred maintenance, structural problems, or other factors that reduce value.
- Error documentation. Proof the assessor used incorrect property characteristics, such as wrong square footage or lot size.
If you disagree with the local board’s decision, most jurisdictions allow a further appeal to a state-level board or an administrative hearing. That stage is more formal, and hiring a property tax attorney or consultant may be worth considering.
How the Bill Gets Paid
If you have a mortgage, your lender likely collects property taxes through an escrow account built into your monthly payment. A portion of each month’s payment goes into the account, and the lender pays your tax bill directly when it comes due. In many cases the bill goes straight to the lender and you never receive it yourself.
Federal regulations require your loan servicer to perform an annual escrow analysis to make sure the account is collecting the right amount. The servicer projects next year’s tax and insurance costs, compares them to what’s already being collected, and adjusts your monthly payment up or down. If your property taxes rise, whether from a reassessment, a new voter-approved levy, or a lost exemption, your monthly payment will rise at the next adjustment to cover it.1Consumer Financial Protection Bureau. 12 CFR 1024.17 Escrow Accounts
If your lender doesn’t escrow property taxes, which is more common with loans that have a low loan-to-value ratio or certain types of financing, you’re responsible for paying the tax bill directly by the deadline. Missing the deadline triggers penalties that build quickly, and unpaid taxes can lead to a tax lien on your property that takes priority over almost all other debts, including your mortgage. Contact your local tax collector’s office early if you’re struggling to pay, since many jurisdictions offer installment plans or hardship programs.