Property tax in the US is a local tax assessed by counties, municipalities, and special districts — never by the federal government. The tax pays for schools, fire, police, libraries, and local infrastructure. It is also the most variable line item in homeownership, with effective rates ranging from under 0.3% (Hawaii) to over 2% (New Jersey, Illinois) of market value, and within a single county, two adjacent homes can have meaningfully different bills.
The two-step calculation
Every property tax bill is the product of two numbers:
Assessed Value × Tax Rate (millage) = Annual Tax
Both inputs vary in ways that surprise new homeowners.
Step 1: Assessed Value
The county assessor sets your property's assessed value, usually annually. Methods vary by state:
- Market-value assessment — assessor estimates current market value (most states).
- Acquisition-value assessment — value is locked at purchase price, capped annual growth (California's Prop 13 — 2% annual cap).
- Fractional assessment — value is set at a percentage of market value (e.g., 35% in some Ohio counties).
The assessed value on your bill is rarely identical to the market value of your home. Equalization rates and assessment ratios further adjust it.
Step 2: The Tax Rate (Millage)
Millage is expressed in mills — one mill = $1 per $1,000 of assessed value. Your total millage stacks contributions from:
- County government
- City or town
- School district
- Community college district (in some states)
- Fire / EMS district
- Library district
- Special assessment districts (drainage, lighting, etc.)
Two homes on the same street can have different millages if one falls inside a special improvement district and the other does not.
Why identical houses can have different bills
- Caps and exemptions: California's Prop 13 caps growth at 2% per year for the same owner. A house held 30 years has an assessed value far below a recently-sold next-door identical home.
- Homestead exemption: most states reduce the taxable value if the property is the owner's primary residence. Florida's homestead is up to $50,000 off assessed value plus a 3% annual cap (Save Our Homes).
- Senior, veteran, or disability exemptions: Texas offers $10,000+ school district exemption for over-65 homeowners.
- Special districts: a Mello-Roos community in California layers an additional bond payment on top of base tax.
- Recent reassessment: in some states, transfer triggers reassessment to current market value.
The escrow flow
If you have a mortgage, your lender almost always escrows property tax: each monthly mortgage payment includes ~1/12 of the annual tax, the lender holds it in an escrow account, and the lender pays the tax bill directly when it comes due.
The escrow analysis happens annually. If property taxes rose 8% but your monthly payment was set at last year's amount, you accumulate an escrow shortage. The lender either spreads the shortage over the next 12 months (raising your payment) or asks for a lump catch-up. Either way, your monthly payment can change without notice.
If you pay cash or your loan does not require escrow, you are responsible for paying the bill directly. Most counties allow installment payment (typically two installments six months apart).
Reading your bill
A typical bill has these sections:
| Field | What it means |
|---|---|
| Parcel / APN | County identifier for your property |
| Assessed Value (Land + Improvements) | Assessor's value, before exemptions |
| Exemptions | Homestead, senior, etc. |
| Taxable Value | What the rate applies to |
| Tax Rate Detail | Each district's millage broken out |
| Total Tax | Sum across districts |
| Special Assessments | Non-millage charges (sewer, lighting bonds) |
| Due Dates | Installment timing |
Pay close attention to the *prior year* column when reading a new bill — material increases without obvious reason are worth investigating.
Challenging your assessment
If you believe your assessment is too high, every state offers an appeal process. Steps:
- Check the deadline — usually 30-60 days after the assessor mails the notice. Miss it and you wait a year.
- Pull comparables — recent sales of similar properties in your neighborhood. Three to five solid comps usually carry an appeal.
- Document condition issues — foundation problems, deferred maintenance, environmental issues.
- File the appeal — informal review first (free), then formal board hearing if needed.
Win rates vary, but a 10-20% reduction is common when comparables clearly support the case. The reduction usually applies for one year only — re-file if needed.
The deductibility limit
Under current federal law (TCJA, in effect through 2025 unless extended), state and local taxes — including property tax — are deductible up to a $10,000 cap per return on Schedule A. In high-tax states (NY, NJ, CA, IL), homeowners often hit the cap quickly.
Property tax is a fact of homeownership in the US. Understanding the calculation, escrow flow, and appeal mechanism turns it from an opaque deduction into something you can actually manage.