Your county valued your whole neighborhood at once
Assessors can't inspect every home, so they value whole neighborhoods at once. They use recent sales, property records and statistical models, a method the industry calls mass appraisal.1
The model only knows what's in the records
A model can't see your kitchen. It works from the facts on file for your home. The mass appraisal standard published by the International Association of Assessing Officers (IAAO) lists characteristics that are usually important in predicting a home's value, including:3
Property recordResidential
Building
- Living area
- Construction quality
- Effective age or condition
- Basements, garages, covered porches
- Bathrooms and central air
Land
- Lot size
Location
- Neighborhood
- View or water frontage
- Nuisances, such as heavy traffic
If a record is wrong or out of date, the model carries the mistake into your value.
The same standard says property characteristics should be verified at least every 4 to 6 years.3 A change made since your home's facts were last checked, such as an addition, may not be on file yet.
Your neighbors' sales move your number
Assessors lean on sales of similar homes nearby. For single-family homes, the IAAO standard calls this method, the sales comparison approach, the best approach.3 When the sales they rely on don't really match your home, your value can land too high.
What makes a sale comparable
California's Board of Equalization gives homeowners three tests:4
- Was it an arm's-length, open-market sale? A sale between relatives may not be.
- Is the home physically similar? Distance, bedrooms and bathrooms, year built, square footage, lot size, condition.
- Did it sell close enough to the valuation date? A California appeals board can't admit comparable sales dated more than 90 days after it.
You're allowed to question it
Homeowners can challenge an assessment, within a deadline their state or county sets.2 The first step is knowing whether your number looks high next to similar homes.
Rules differ by state, so check yours before you file. Your assessment notice lists yours.
You can also ask how the number was reached. Under the IAAO standard, assessment staff should at least be able to produce a property record and explain the approach used.3
A property owner should never be told simply that “the computer” or “the system” produced the appraisal.
Before a hearing in Texas
- At least 14 days before a protest hearing, the chief appraiser must tell you that you can request, free, the data, schedules and formulas they will introduce at the hearing.6
- You can also protest on the ground of unequal appraisal. One of the tests in that protest is whether your appraised value is equal to or less than the median appraised value of a reasonable number of comparable properties, appropriately adjusted.7
