What Is Comparable Sales
Comparable sales are recent arm's-length transactions of properties similar to yours in location, condition, size, and features. Assessors use these sales to establish market value, which forms the basis of your property tax assessment. In a property tax appeal, comparable sales data becomes your primary weapon to challenge an inflated assessment.
Why It Matters in Appeals
Most jurisdictions use the Sales Comparison Approach as their primary valuation method, making comparable sales the cornerstone of assessment justification. When you file a board of review appeal, the assessor will present comparable sales to support their valuation. If those comps don't actually match your property or contain methodological errors, you can use better comps to prove the assessment is too high.
The assessment ratio in your county matters here. If your county assesses properties at 100% of market value versus 50%, the same comparable sale has different implications. A $500,000 comp sale might justify a $400,000 assessment in a 80% assessment ratio jurisdiction, but only a $250,000 assessment in a 50% ratio jurisdiction.
Selecting Strong Comps
Not all sales qualify as valid comparables. Your strongest comps share these characteristics:
- Sold within 12 months of your assessment date (some jurisdictions accept up to 18 months in slower markets)
- Located in the same neighborhood or subdivision, or in a directly comparable market area
- Similar square footage (typically within 10-15% of your property)
- Equivalent lot size and topography
- Same or very similar age and condition
- Comparable utility, parking, and access features
- Arm's-length transactions (not sales between related parties, foreclosures, or distressed sales)
A $550,000 sale of a 2,200 sq ft home two blocks away carries far more weight than a $600,000 sale of a 3,500 sq ft home ten miles away. Quality of comps matters more than quantity.
Adjustments and Their Limits
When comps aren't perfect matches, you apply Adjustment factors to account for differences. If your comp sold for $450,000 but has a finished basement your property lacks, you might subtract $15,000 to $25,000 depending on local market data. However, cumulative adjustments exceeding 15-20% of the comp's sale price begin losing credibility before a board of review. Excessive adjustments suggest you're forcing weak comps into service.
Using Comps in Board of Review Hearings
At a board of review hearing, present your best 3 to 5 comps with clear supporting documentation. Include copies of MLS listings, property record cards showing lot size and square footage, photos, and any public information about condition. Calculate your subject property's indicated value by averaging the adjusted comp prices. If assessor comps show $425,000 average value but your better-selected comps average $385,000, request the assessment be reduced to align with current market data.
Where to Find Comparable Sales Data
- County recorder or assessor's office (public records of sale prices and property details)
- MLS systems (if you have agent access or use third-party MLS search tools)
- Tax assessment websites showing recent sales in your area
- Real estate websites like Zillow or Redfin (use with caution for older data)
- Professional appraisers (if you hire one to strengthen your appeal)
Common Questions
- Can I use a comp that sold 18 months ago if no recent sales exist? Yes, in slower markets or rural areas, many jurisdictions accept sales up to 18-24 months old. Check your county's specific guidelines, but be prepared to explain why newer comps aren't available and how market conditions have changed since that sale.
- What if the assessor's comps are better than mine? Request detailed adjustment schedules from the assessor. Challenge the adjustments themselves rather than the comp selection. Question whether adjustments reflect actual market data or are inflated estimates. Sometimes the assessor's comps are solid, meaning your assessment may be defensible.
- Do I need a professional appraisal to appeal using comparables? No. You can present comps yourself at a board of review hearing. However, an independent appraisal ($300-$800) adds credibility if your self-selected comps differ significantly from the assessor's valuation.