How many comps do I need? How close? How recent?

Boards weigh comparable sales more heavily than almost any other evidence, but the standard is about quality and similarity, not volume.

How many. Three to five strong comparables is the widely accepted target. New Jersey codifies this: its Division of Taxation appeal guidance and the Form A-1 comparable-sales schedule call for a minimum of three and a maximum of five comparable sales attached at filing. Three excellent comps that closely match your home beat ten mediocre ones — extra weak comps invite the board to pick apart your case.

How recent. Use arm's-length sales that closed within roughly 12 months of your jurisdiction's valuation (lien) date — January 1 in most states, October 1 in New Jersey. Older sales may still be admissible but carry less weight and may need a time adjustment for market movement. The closer to the lien date, the stronger.

How close (similarity). A good comp matches the subject on the factors that drive value:

• Location — same neighborhood, subdivision, or school attendance zone wherever possible.
• Size — living area within roughly 10–20% of your square footage.
• Type and age — same style (ranch vs. two-story), comparable year built, similar lot size.
• Condition and features — similar updates, garage, bedroom/bath count.

Where a comp differs, you adjust for the difference (e.g., dollars-per-square-foot for size), which is exactly how mass-appraisal systems value property — see the IAAO Standard on Mass Appraisal of Real Property.

Use only arm's-length sales. Exclude foreclosures, family transfers, and other non-market deals — the IAAO defines market value by the arm's-length, open-market standard, and assessors discount sales that aren't.

Bottom line: pick three to five recent, nearby, similar arm's-length sales, adjust for any differences, and present the tight set — depth of match wins over breadth of list.