Property Tax Assessment
A property tax assessment is your local government’s official valuation of your home for the purpose of calculating how much property tax you owe — and it’s frequently wrong, costing homeowners an average of $1,200/year in overpayments.
Your county assessor determines your home’s assessed value. Then your local tax rate (called a mill rate) is applied to that value to calculate your annual tax bill. For example: a home assessed at $300,000 with a mill rate of 1.2% owes $3,600/year. Simple math, but the assessed value is where things get messy.
How Assessments Work
Most counties reassess properties every 1-5 years. The assessor uses comparable sales, property characteristics, and sometimes a physical inspection to determine value. But here’s the catch: assessors are evaluating thousands of properties with limited staff. They make mistakes. Studies show that 30-60% of properties are over-assessed at any given time.
Some states assess at 100% of market value, others at a fraction. In Ohio, properties are assessed at 35% of market value. In South Carolina, owner-occupied homes are assessed at just 4%. Your assessed value and your market value are not the same thing — and the ratio between them matters enormously for your tax bill.
The Cost Impact
Property taxes are the single largest recurring cost of homeownership after the mortgage. The national average is $2,690/year, but it varies wildly. New Jersey averages $9,500+/year. Hawaii averages under $700. Use the property tax calculator to estimate what you’ll owe in your area.
An over-assessment of just 10% on a $350,000 home costs you $420-$1,000+ per year depending on your tax rate. Over 10 years, that’s $4,200-$10,000 in unnecessary taxes. Most homeowners never check — and the assessor isn’t going to volunteer that you’re overpaying.
How to Appeal
Every county has a formal appeals process. You’ll need comparable sales data showing your home is worth less than the assessed value. The appeals window is typically 30-90 days after you receive your assessment notice. Don’t miss it — once the deadline passes, you’re stuck until the next reassessment.
The appeal process is free in most counties. Gather 3-5 comparable sales (similar homes that sold recently for less than your assessed value), note any condition issues the assessor may have missed, and present your case at the hearing. Success rates range from 25-50%, with average reductions of $10,000-$50,000 in assessed value.
Watch out: Buying a home can trigger a reassessment to the purchase price, even if the previous owner had a much lower assessed value. In California (Prop 13), the base year value resets to the purchase price at sale. That $4,000/year tax bill the seller was paying could become $8,000+ for you overnight. Factor this into your home buying budget.
According to the CFPB, property taxes are part of your monthly escrow payment and directly affect your total housing cost. Lenders analyze your tax obligation when determining how much you can borrow.
How often should I check my property tax assessment?
Every single year. Even if your county only reassesses every 3-5 years, changes in local tax rates can still increase your bill. Review your assessment notice as soon as it arrives and compare it to recent sales in your neighborhood. If your assessed value seems too high, appeal immediately — the deadline won’t wait.
Can my property tax assessment go down?
Yes. If home values in your area decline (like during a recession), your assessed value should drop too. But assessors are slow to reduce values — they’re much faster at increasing them. If the market drops and your assessment doesn’t, that’s a strong appeal case. Bring market data showing comparable sales below your assessed value.