County assessor data — how millage rates and assessments actually combine

Assessment vs. market value

Assessed value is what the county tax assessor decides your property is worth — not what Zillow says or what you'd sell for.

Many states cap year-over-year assessment growth (California's Prop 13: 2%/yr; Florida Save Our Homes: 3%/yr). That's why long-term homeowners pay less than identical neighbors who just bought.

When you buy, the property typically reassesses to sale price. Budget for the higher tax, not the seller's last bill.

Millage rate (or mill levy)

1 mill = $1 of tax per $1,000 of assessed value. A 25-mill rate on a $300k assessment = $7,500/year.

Millage stacks: school district + county + city + special districts (water, fire, library) all add their own mills, summing to your effective rate.

School-district mills are usually the biggest line — often 50–70% of the total.

Exemptions

Homestead exemption (most states): reduces taxable assessment for owner-occupants. Sizes vary wildly — Florida $50k, Mississippi $7,500, Texas $100k for school taxes.

Senior, veteran, disability exemptions add on top in many states. Apply for them — they don't auto-apply.

When you buy, the prior owner's homestead doesn't transfer. Apply yourself in the first eligible window or you'll lose a year.

Why assessors matter

Assessment ratios (the % of market value that becomes assessed value) vary by state and class — residential vs. commercial, agricultural vs. urban.

If your assessment looks too high relative to comparable sales, every county has an appeal process. Statistics suggest ~30–40% of well-prepared appeals succeed.

What zipradar shows

Median assessed value, effective millage rate, total median tax bill for the ZIP, plus deep-link to the county assessor's detail page for parcel-level lookup.

Top 50 metros covered in v1; rolling out to top 100 by Q3. State-level rollups for areas not yet parcel-mapped.