How Property Tax Reassessment Works

A notice of reassessment arriving in the mail is often a source of anxiety for homeowners. A higher assessed value usually means higher property taxes. But how exactly does the assessor decide your home is worth more, and when are they allowed to do it?

What is Reassessment?

Property tax is an ad valorem tax, meaning it is based on the value of the property. For the tax to be fair, the assessed value needs to accurately reflect the property's current market value. Reassessment is the process local governments use to update property values on the tax rolls.

When property values in a neighborhood rise, a reassessment captures that appreciation. Without periodic reassessments, new homeowners would pay significantly more than long-time residents in identical homes, creating an inequitable tax burden.

When Does Reassessment Happen?

The schedule for reassessment is dictated by state and local laws, and it falls into three main categories:

• Cyclical Reassessment: The jurisdiction reassesses all properties on a fixed schedule. For example, Colorado reassesses every two years (odd years). Maryland assesses properties on a three-year cycle. Some states mandate a cycle but allow counties to choose their own schedule within certain limits.
• Triggered Reassessment: Properties are reassessed only when a specific event occurs, most commonly a change in ownership (selling the home) or new construction (pulling a permit for an addition). California's Proposition 13 is the most famous example of this system.
• Annual Reassessment: Some jurisdictions update values every single year using statistical models based on recent sales data in the area.

How Assessors Determine the New Value

It is a common misconception that the tax assessor drives by every house to determine its value. In reality, assessors use a process called mass appraisal.

Mass appraisal relies on statistical modeling. The assessor's office collects data on all recent property sales in a neighborhood. They feed this sales data into a computer model along with the characteristics of the unsold homes (square footage, age, lot size, number of bathrooms, etc.). The model then estimates the current market value of all homes in the area based on what similar homes recently sold for.

Because it relies on algorithms and public records, mass appraisal is efficient but prone to errors for individual properties. If the county records incorrectly show your home has four bedrooms instead of three, or if they missed that your basement flooded and hasn't been repaired, your reassessed value will likely be too high.

The "Tax Rate Trap"

When homeowners receive a notice that their assessed value increased by 20%, they often panic, assuming their tax bill will also increase by 20%. This is usually not the case due to how tax rates are set.

Local governments calculate their budget needs first. They then divide that budget by the total assessed value of all properties in the jurisdiction to determine the tax rate. If everyone's property value goes up by 20% due to a county-wide reassessment, the local government can lower the tax rate and still collect the same amount of revenue.

Your tax bill will only increase drastically if your property's value increased significantly more than the average property in your jurisdiction, or if the local government explicitly raised its budget.

Caps on Assessment Increases

To protect homeowners from sudden tax shocks in rapidly appreciating markets, many states have implemented caps on how much an assessed value can increase in a single year, regardless of market value.

• Florida (Save Our Homes): Caps annual assessment increases on primary residences at 3% or the inflation rate, whichever is lower.
• Texas: Caps annual increases on homesteads at 10%.
• New York: Caps increases at 6% in a single year and 20% over five years (for certain property classes).

These caps create a gap between your home's actual market value and its assessed value. However, these caps almost always reset to the full market value when the property is sold.

What to Do When You Get Your Notice

When the reassessment notice arrives, do not ignore it. You only have a limited window — often just 30 to 45 days — to file an appeal if you disagree with the value.

First, check the property details listed on the notice or your property record card online. Look for factual errors regarding square footage, room count, or acreage. Second, look at recent sales of comparable homes in your neighborhood. If they sold for significantly less than your new assessed value, you have strong grounds for an appeal.