How to Use Comps to Appeal Your Property Tax
By The HomeHubAI Team · · 8 min read
You opened the assessment notice and the number felt high. Maybe you just bought the house and the county already has you above what you paid. Maybe the market cooled and the roll did not.
Appeals are rarely won by saying the tax bill hurts. They are usually won with a short list of closed sales that look like your house, sold near the date the county used, with the differences spelled out in a table.
A Zestimate will not do that work for you. A comps table will. HomeHubAI does not file appeals, and this is not legal advice. It is a practical way to assemble the evidence most boards actually look at.
Assessed value and market value are different numbers
Your assessed value is the figure the assessor put on the roll for tax purposes. Market value is what a willing buyer would likely pay a willing seller, on the open market, around a specific date.
Those two numbers can sit apart for boring reasons. Some states lock in a base year and only reassess after a sale or new construction. Some counties update on a cycle that lags the market. Mass-appraisal models treat a block as more uniform than it is. A recent purchase can also trigger a new assessment that sits above later sales.
If the assessed value is above what similar homes actually sold for around the valuation date, that gap is the case. You still have to prove it with sales.
Find the valuation date and the filing deadline
Before you collect comps, find two dates on the notice or the assessor's site: the valuation date (sometimes called the lien date), and the last day you can file.
Those dates are local. Do not trust a national checklist. Your county assessor or assessment appeals board publishes them.
The valuation date matters more than people expect. You are arguing about value on that day, not today. A sale from last week can be too late. A sale from two years ago can be too early, or it can be fine if you explain the time gap.
San Francisco is a useful example, not a national rule. The city's Assessment Appeals Board says it may only consider comparable sales that closed no later than 90 days after the valuation date. Sales well before that date, or up to 90 days after, can come in. Sales closer to the date are treated as more reliable. For a January 1 decline-in-value appeal, that 90-day window ends March 31.
Your county may use a different window. Read theirs.
Which sales to bring
Most residential appeals live or die on comparable sales. San Francisco's board calls that approach the most reliable evidence for a house. Washington's Board of Tax Appeals says the same for residential property, and it wants those sales in a grid.
A practical packet for a house is three to five closed sales. That is also the floor Fannie Mae sets for a mortgage appraisal: at least three closed comparables. An appeal is not an appraisal, and your board may want more or fewer. Three to five similar sales is a workable start. One sale looks like a cherry-pick. A dozen weak ones give the assessor more to poke at.
Each sale should be:
- Closed. A listing is an ask. It does not show what a buyer paid.
- Similar. Same property type, close in size, age, bedrooms, and condition.
- Nearby. Same neighborhood or subdivision if you can get it.
- Close to the valuation date. Check your county's window before you fall in love with a recent closing.
- Arm's-length. Relatives, rushed sellers, and off-market deals can land at the wrong price. San Francisco's board asks whether the house was exposed on the open market.
Leave out distressed sales when you can. Foreclosures, REO, and short sales often trade below a normal market sale because the seller is under pressure or the house needs work. Washington's tax appeal board says those are usually not considered normal market sales. HomeHubAI drops them from estimates for the same reason.
If a distressed sale is the only nearby data point, say so and explain the condition. Do not treat it as interchangeable with a regular sale.
Adjustments are how you explain the leftovers. If a comp has a pool and you do not, say the sale is a bit high for that reason. If yours is smaller, say so. You do not need an appraiser's form. You need a sentence the board can follow. Time, flood zone, schools, and condition are the same kinds of differences a HomeHubAI report already adjusts for. Seller concessions can also sit inside a recorded price. A raw price per square foot skips most of that.
Put the evidence in a table
Boards read tables faster than a stack of printouts. Washington's board publishes a sales-grid template for that reason. Keep yours short: the subject house on the first row, then three to five sales, then a one-paragraph argument.
| Address | Sale date | Price | Beds / baths | Sqft | Year | Notes |
|---|---|---|---|---|---|---|
| Your house (subject) | — | Assessed $468,000 | 3 / 2 | 1,620 | 1988 | The property under appeal |
| 18 Cedar Ave | Nov 8 | $418,000 | 3 / 2 | 1,590 | 1991 | Similar condition, one block over |
| 41 Birch St | Dec 2 | $405,000 | 3 / 1.5 | 1,540 | 1985 | One fewer half bath |
| 9 Maple Ct | Jan 20 | $422,000 | 3 / 2 | 1,710 | 1990 | Larger; treat as a high indication |
Then one paragraph, in your own words. Something like:
As of the January 1 valuation date, three nearby three-bedroom houses of similar size and age sold between $405,000 and $422,000. The assessed value of $468,000 sits above those sales. Comp 3 is 90 square feet larger, so I treated it as a high indication. None of these were foreclosure or short sales.
Photos of a tired roof, a dated kitchen, or a foundation crack help if condition is part of the argument. A contractor bid is better than a complaint. Washington's board is explicit: do not just say repairs are needed. Show the work and the cost.
What not to rely on
A Zestimate is one model's number. It is not a recorded sale and not an appraisal, and you cannot show the sales behind it. Boards ask for comparable sales they can inspect. Bring those. Use an automated estimate only to find candidate addresses, then verify each closing in official records or MLS.
Active listings and list prices are asks. They are not what a buyer paid. In some neighborhoods the ask and the sale sit far apart. We wrote about that on a Sunset house that listed at $949,000.
A neighbor's assessed value is also a weak exhibit. Washington's board says it generally cannot use that, or your own assessed value from other years. A neighbor's sale price can help if the house is comparable and the sale is timely.
Texas and other non-disclosure states
You still have a path. Texas Government Code § 552.149 lets the owner or agent request the appraisal district's hearing evidence and a reasonable number of comparable sales relevant to the protest. That data stays confidential and is for the hearing, not for posting online. You can also hire an appraisal, or ask an agent to pull closed MLS sales.
Do not assume a public website can replace those sources in Texas. It cannot see prices the county itself treats as confidential.
What a HomeHub report already shows
If you are in a market where sale prices are public, run a free HomeHubAI report. You get an estimate, a range, a confidence score, and the comparable sales we used. Distressed transfers are dropped. Remaining sales are adjusted for time, flood risk, schools, and how similar the home is. That is already the shape of a comps table.
Check each sale date against your county's rule. A report run today is aimed at current value. Your appeal is aimed at the assessor's date. If a sale sits outside that window, leave it out or explain why you kept it.
The report is a starting packet, not a filing. We do not submit it for you, and it is not an appraisal.
- Run a free valuation and read the comps, the range, and the adjustments.
- Browse public home value estimates by city, neighborhood, or ZIP.
- Open the home value map to look at estimates nearby.
Questions we get
How do I appeal a property tax assessment? Read the notice for the valuation date and the filing deadline, then file with your county assessor or appeals board using their form. Bring a short list of closed, similar sales near that date, a simple comps table, and a one-paragraph argument. Deadlines and forms are local. This is not legal advice, and HomeHubAI does not file appeals.
How many comps do I need for a property tax appeal? Three to five closed, truly similar sales is a workable residential packet. A mortgage appraisal usually shows at least three closed comparables. Your board may accept fewer in a thin market or want more. Quality beats a long list of weak matches.
Why isn't a Zestimate accepted by an appeal board? A Zestimate is one model's number. It is not a recorded sale and not an appraisal, and you cannot show the sales behind it. Boards ask for comparable sales they can inspect. Use automated estimates to find candidate addresses, then verify each closing in official records or MLS.
What if I live in Texas or another non-disclosure state? Sale prices are not public in non-disclosure states such as Texas, so HomeHubAI cannot show comps in every market. Ask the appraisal district for the evidence it will use and for comparable sales relevant to your protest, hire an appraisal, or ask an agent for MLS closed sales.
Does HomeHubAI file property tax appeals? No. HomeHubAI does not file appeals, is not a tax consultant, and this guide is not legal advice. A report is a comps table you can read and, where sale prices are public, bring as a starting point.
What if my assessed value is higher than market value? That gap is the usual reason to appeal. Prove it with closed sales around the valuation date, not with the size of the tax bill. Check your local filing window first.