Comparable Sales (Comps)

Comparable sales, or "comps," are recent open-market sales of homes similar to yours in size, age, location, and condition. They are the primary evidence in the sales comparison approach to value — and the single most persuasive thing you can bring to a property tax appeal. The logic is simple: if homes like yours are selling for less than your assessed value, your assessment is probably too high.

Why comps matter

Assessors and appeal boards both lean on the sales comparison approach, which the assessment profession treats as the preferred method for valuing residential property. It estimates your home's value by looking at what genuinely similar properties actually sold for — not asking prices, not online auto-estimates, but closed sales. A strong set of comps turns "I think my taxes are too high" into a documented, defensible number.

How comps are adjusted

No two homes are identical, so each comp is adjusted up or down for its differences from yours. A comp with an extra bathroom, a finished basement, or a better view is adjusted downward before comparison; one in worse condition or with less living area is adjusted upward. Appraisers typically compare on a price-per-square-foot basis of living area. The goal is an apples-to-apples figure that reflects what your specific home would have sold for.

What makes a comp strong

A few solid comps beat a long list of weak ones. The best comps are close to your home geographically, similar in physical characteristics, genuine arm's-length sales (not foreclosures or family transfers), and — critically — close in time to the assessor's valuation date. Many jurisdictions limit how far after that date a sale can be and still count, so timing matters as much as similarity.

How it affects your appeal

In an appeal, your comps are the evidence that your assessed value exceeds your market value. Boards weigh how comparable each sale is and how well you've adjusted for differences. A clean, well-adjusted comp grid is what separates a winning appeal from a hopeful guess.

Related

• What is an over-assessment?
• How assessors value your home
• How to appeal property tax
• Assessed Value vs Market Value
• Reassessment
• Run a free over-assessment check

Sources

• IAAO — Standard on Mass Appraisal of Real Property (sales comparison approach; market value definition; sale validation): https://www.iaao.org/wp-content/uploads/StandardOnMassAppraisal.pdf
• IAAO — General Assessment FAQs: https://www.iaao.org/industry-data/general-assessment-faqs/