Property Taxes Explained: Assessment, Millage, and Exemptions

Your property tax bill is produced by two organizations that don't talk to each other much and are legally forbidden from doing each other's job. One decides what your house is worth. The other decides what percentage of that to charge. Almost every complaint people have about their bill is aimed at the wrong one.

Sort out which is which and the bill stops being weather and starts being arithmetic you can argue with.

Value times rate, and both halves move

The formula is the same everywhere, though the vocabulary changes at every state line. Florida's Department of Revenue states it as cleanly as anyone: "Millage is a tax rate defined as the dollars assessed for each $1,000 of value; one mill is one dollar per $1,000 of assessed value. Mathematically the equation is: Taxable value ÷ 1,000 × millage rate = Property Tax Owed."

So a house with $250,000 of taxable value in a jurisdiction levying 18.5 mills owes $250,000 ÷ 1,000 × 18.5 = $4,625. Some states quote a percentage rate instead of mills, and some quote dollars per $100. Same equation.

The two halves come from different offices. In Florida, the property appraiser "determines the taxable value of each property in the county," and the department is explicit that "Property appraisers do not set millage rates." Rates come from taxing authorities — county governments, school boards, municipalities, water management and special districts — each adopting a budget and levying a millage to fund it. Your bill is the sum of several separate levies you never voted on individually.

Market value, assessed value, taxable value

Three numbers, routinely confused, and the difference between them is where the money is.

Market value is what the house would sell for. Texas taxes on it directly: the Comptroller says "taxing units must tax all property based on its current market value. That's the price it would sell for when both buyer and seller seek the best price."

Assessed value is what the state's rules say to write down. Plenty of states apply a fixed ratio to market value rather than using it whole. Ohio's administrative rule sets taxable values at "thirty-five per cent of the current true value." A $300,000 Ohio house carries $105,000 of taxable value. That does not make Ohio cheap — the millage rates are built around the ratio — but it does mean an Ohio homeowner comparing their assessment to their neighbor's Zillow estimate is comparing two unrelated numbers.

Taxable value is assessed value after exemptions come off. It's the only one the formula actually uses, and it's the one most people never look at.

Exemptions: the largest number most homeowners leave on the table

The Texas Comptroller frames the default: "All property is taxable unless federal or state law exempts it from the tax. These exemptions may exclude all or part of your property's value from taxation."

A homestead exemption is the big one — a reduction available on your primary residence, and only your primary residence. Florida's is worth as much as $50,000 off taxable value. Run that through the same math: $250,000 of assessed value in an 18.5-mill jurisdiction drops to $200,000 taxable, and the bill goes from $4,625 to $3,700. Nine hundred and twenty-five dollars a year for filing a form once.

Other exemptions stack on top, and the categories are broadly familiar even though the amounts and rules are entirely local: age 65 or older, disability, veterans and surviving spouses, agricultural use, and in some places energy improvements or historic designation.

The failure mode is universal. Exemptions almost always require an application, they usually have a filing deadline tied to a specific date early in the year, and they generally do not transfer from the previous owner. Nobody will call to tell you that you qualified and missed it. Look up your county assessor's exemption page this week, not next spring.

Why the bill jumps the year after you buy

This is the single most common shock in homeownership, and it produces a lot of accusations of fraud that aren't fraud. There are three separate mechanisms, and in a bad year all three fire at once.

1. The previous owner's exemptions come off. If they had a homestead exemption, a senior exemption, and a veteran's exemption, all of that disappears with them. Yours has to be applied for, and often can't take effect until the following tax year.
2. Assessment caps reset. Many states limit how fast a long-term owner's taxable value can rise, and the cap resets on a change of ownership. California is the clearest case: Revenue and Taxation Code 110.1 sets a base year value as of the date the property is purchased or changes ownership, and Section 51 limits the annual inflation adjustment to that value so that the increase cannot "exceed 2 percent of the prior year's value." A neighbor who bought in 1998 has decades of suppressed value. You start over at today's price.
3. Your purchase price is now the best evidence anyone has of market value. Assessors are looking at recent sales, and yours is the most recent one on the street.

None of this is discretionary and none of it is aimed at you. It also means the seller's tax bill — the number that was on the listing, the number your lender may have used to build your escrow estimate — is close to worthless as a forecast. Ask the county assessor what your bill would look like at your purchase price with only the exemptions you'll actually qualify for. Getting that wrong is the number one cause of the escrow shock this site covers separately, where the payment jumps by more than the tax increase because the servicer has to fund a shortage and a higher monthly estimate in the same twelve months.

A lower rate does not mean a lower bill

Florida's department answers this one directly. Asked whether a lowered millage rate means a lower bill: "Not necessarily. There are several factors which can cause your tax bill to increase even if a taxing authority decreases its millage rate." If your taxable value rose, it can swamp the rate cut. If other taxing authorities raised their rates, the total still climbs. And previously deferred value under an assessment cap can push your taxable value up even in a flat market.

Which is why the rolled-back rate is the number to look for on your notice — the rate that would raise the same revenue as last year given the new values. A jurisdiction adopting a rate above the rolled-back rate is raising taxes even if the millage number went down.

Read the notice, not the bill

By the time the bill arrives, the arguing is over. The document that matters comes months earlier — Florida calls it the Notice of Proposed Property Taxes, or TRIM notice, and it carries each taxing authority's proposed budget and millage, the rolled-back rate, the taxes you'd owe if the proposal is adopted, and any non-ad valorem assessments.

It also carries your deadline. Florida's schedule is typical of the shape: tentative millage rates for most taxing authorities are set before August 5, final rates are adopted in September, and school districts run earlier, adopting in July. Public hearings happen in that window and you can show up to them. Your state's calendar differs; the structure rarely does.

Three things to check the day the notice lands: that the square footage, bedroom count, and lot size on your property record are correct; that every exemption you qualify for is showing; and that your assessed value is in line with what comparable homes nearby actually sold for. If the third one is off, this site has a full walkthrough of appealing an assessment, including the evidence that moves review boards and the deadlines that end the conversation.

Don't pay a company a third of your savings

Property tax consultants who work on contingency will happily take 30 to 50 percent of your first-year reduction for filing a form and attaching three comparable sales. In a straightforward residential appeal, that's work you can do in an evening with your county's own online sales search — the informal review stage in most jurisdictions is a conversation, not a hearing.

Hire someone when the property is commercial, when the value is genuinely contested and large, or when the appeal has escalated past the informal stage into something adversarial. Not for a $300,000 house and a $4,000 bill.

Do this now: find your parcel on the county assessor's website, open the property record card, and check the exemptions line. If it's blank and the house is where you sleep, you have found money — and a form with a deadline on it.