NASSAU COUNTY HOMEOWNER RESOURCES

Choosing comparable sales for a Nassau County grievance

An appeal is an argument about value, and comparable sales are how that argument is usually made. A few well-understood sales beat a long list you cannot explain.

By Good Grieves · Sources reviewed September 20, 2026

What you are actually arguing

Nassau County defines market value as “the most probable price at which a property would sell if offered for sale under ordinary circumstances.” A comparable sale is useful to the extent it stands in for that — a real transaction, close enough to your home in the ways that drive price, that a reader can accept it as a proxy.

Note the phrase ordinary circumstances. A sale between relatives, an estate sale, or a foreclosure may be a real transaction and still be a poor comparable.

Start with the differences that move price

When you line a sale up against your home, work through these in order:

1. Property type and style. Compare like with like before anything else.
2. Living area. Usually the single largest driver. A meaningful size gap is hard to argue past.
3. Location. Same school district and same neighborhood, ideally. Proximity on a map is not the same as comparability.
4. Age and condition. Often the weakest data you will have, and the most likely to be challenged.
5. Sale date. A recent sale reflects the market you are arguing about; an older one may not.
6. Lot and setting. Lot size, corner or through lots, and obvious external factors.

Write down what does not match

The instinct is to present only flattering sales. Resist it. A comparison you have annotated honestly — “larger by roughly 300 square feet, sold fourteen months ago, renovated kitchen per the listing” — is more persuasive than an unqualified list, and it prepares you for the obvious questions.

Keep a short record for each sale: the address, the sale date and price, where you found it, and the two or three differences from your home. If condition or renovation history is unknown, write that it is unknown. An open question is a legitimate entry; an assumption presented as a fact is not.

A neighbor’s lower tax bill is not a comparable

This is the most common mistake, and it is worth stating plainly. Different exemptions and different taxing districts produce different bills for similar homes, so a bill comparison does not establish that your assessment is wrong. Our exemptions guide explains why two neighbors can be taxed differently on purpose.

The same caution applies to assessed values pulled from different years. Compare matching periods and matching measures, and label both.

How many sales, and how recent

There is no magic count. Three or four sales you can discuss in detail are more useful than a dozen you cannot. Prefer the most recent sales that are genuinely similar over older sales that match perfectly on paper — and if the only close matches are old, say so rather than hiding it.

Using the Good Grieves checker

Our property checker brings available County assessment records, property details, and sales context into one view so you can start this comparison from records rather than from memory. Coverage varies, and a missing record is not a zero — check the year and source labels, and verify anything important with the County.

The checker shows available records; it does not perform an appraisal, and it does not decide which sales are comparable. That judgment stays with you, or with a professional you engage.

Then put it on the calendar

Evidence is only useful inside the filing window. Read the deadline guide for the published dates and the process guide for what follows a filing. Savings are not guaranteed, and this page is general information rather than an appraisal or legal advice.