How to compare condo assessments to identical units in your building

Last updated 2026-07-10

Why comparing your condo to identical units is the strongest appeal argument you have

Most condo appeals fail not because the owner was wrong, but because they argued the wrong thing. They show up with a Zillow printout and argue market value, when the assessor is already running a mass-appraisal model that ignores individual quirks. The argument that lands is equity: your unit is assessed higher than comparable units in the same building without a valid reason.

Property tax law in most states requires "uniform and equal" treatment of similar properties. In Texas, Texas Tax Code Section 41.43 protects the right to appeal on grounds of unequal appraisal, meaning your assessed value is higher than the median level of appraisal of a sample of comparable properties. ^[1] Illinois, New York, and most other states have equivalent provisions under their assessment uniformity doctrines.

Condos make this argument unusually clean. Identical floor plans on the same floor, built the same year, with the same finishes and the same HOA, should carry the same assessed value. When they don't, you can show it in a single table with public data. Boards of equalization respond to that. It's hard to defend a 20% spread between unit 4B and unit 7B when the assessor's own records show the same square footage and the same building class.

This is different from arguing your condo is worth less than the assessed value. You might win that argument too, but it requires an appraisal, comparable sales analysis, and more time. The equity argument needs only the assessor's own data, which is free and public.

Where do you find assessment data for every unit in your building?

Your county assessor's public records are the starting point. Almost every county in the U.S. now runs an online portal where you can search by address or parcel number. For a condo building, every individual unit is a separate parcel with its own assessed value, and all of them sit in that database.

Here's how to get the full list:

1. Go to your county assessor's website and search for your building's street address rather than your unit number. Many portals return all parcels at that address in one result set. 2. If the portal only shows one unit at a time, search for your unit, then note the parcel number format. Condo parcels in most counties are numbered sequentially or by unit designation. Increment through them manually or ask the assessor's office for a bulk export. 3. Some counties publish downloadable assessment rolls as CSV or Excel files. Cook County, Illinois publishes its entire assessment roll publicly. ^[2] Los Angeles County's assessor portal lets you search by situs address and returns all units. ^[3] If yours doesn't, a public records request (often called a FOIA request at the federal level, with state equivalents) will get you the data within a few business days at no cost. 4. Once you have the list, record: unit number, square footage (if shown), assessed value, and floor level.

If you live in a city with its own assessment authority rather than a county system, look there instead. New York City's assessment data is available through the NYC Department of Finance's property search tool, and you can pull every unit in a building by address. ^[4] The data is public by law in every state.

One practical shortcut: many HOA management companies have already compiled unit specs for the whole building. Your building manager or HOA board may hand you a unit list with square footages, which saves you from reconstructing that from assessor records alone.

How do you group units so you're comparing the right ones?

Not every unit in the building is actually comparable to yours, and grouping wrong will sink your appeal. Assessors and appeal boards push back if you're comparing a studio to a two-bedroom or a parking-level unit to a penthouse.

Group by these factors in order of importance:

Factor	Why it matters
Floor plan / unit type	Square footage and layout drive value more than anything else
Floor level	Higher floors typically carry a premium; keep each tier separate
Exposure / view	Corner units or park-facing units may legitimately differ
Building wing	Some buildings have A and B wings with different finishes or vintage
Parking included	A deeded parking space can add assessed value legitimately

In most mid-rise condo buildings, the realistic comparison group is your floor plan type across several floors in the middle of the building, excluding penthouses and basement-adjacent units. That's often 8 to 20 units depending on building size.

If your building has only one floor plan (common in converted warehouse lofts or small co-ops), then every unit is comparable and your job gets simpler. If it has six floor plans, isolate just yours.

Some assessors define unit tiers right in their records. In Chicago's condominium mass appraisal model, the Cook County Assessor groups units by class code and exterior story range. ^[2] Knowing how your assessor grouped units lets you argue on their own terms.

How do you calculate whether your assessment is out of line?

Once you have your comparison group, the math is short. Calculate assessed value per square foot for each unit, find the median for the group, and compare your unit's rate to that median.

Example: You have a 950 sq ft unit assessed at $320,000. Eight identical-plan units in the same mid-rise range from $255,000 to $290,000, with a median of $272,000. Your per-square-foot rate is $336.84. The median is $286.32. You're 17.6% above the median of your own comparison class.

That 17.6% gap is your headline number for the appeal. Texas Tax Code Section 41.43 allows an unequal appraisal protest if your value exceeds the median level of appraisal of comparable properties by more than the median absolute deviation of the sample. ^[1] Most other states use a simpler test: show the gap is material and unexplained.

What counts as "material" varies. Many appeal boards treat anything under 5% as noise. A gap above 10% starts getting attention. Above 15-20%, the burden effectively shifts to the assessor to explain why.

Three numbers go in front of the board: your assessed value per square foot, the median assessed value per square foot for the comparison group, and the percentage difference. Keep it to one page. Boards reviewing 200 cases a day respond to clarity, not volume.

If your county publishes an equalization ratio (the ratio of assessed value to actual market value), you can also check whether your unit's implied ratio runs higher than the countywide ratio. The International Association of Assessing Officers publishes standards on acceptable assessment uniformity, including that the coefficient of dispersion for residential properties should be 15% or less. ^[5] Blowing past that standard inside your own building is a secondary argument worth one sentence in your filing.

What physical differences between units could justify a higher assessment?

Before you file, be honest with yourself about whether there's a real reason your unit is assessed higher. Assessors aren't always wrong. Here are the common legitimate reasons a unit carries a higher value within the same floor plan.

View premium. A unit facing Central Park or the ocean legitimately commands more value than an interior-facing unit of the same size. If your building's records show view tier coding, check whether your unit was actually coded as premium.

Renovation permits. If the previous owner pulled permits for a kitchen or bath remodel, those can appear in the assessor's file and bump the value. Check your permit history through the building department.

Balcony or terrace square footage. Some assessors fold outdoor space into assessed value at a fraction of interior square footage. If your unit has a terrace and others don't, some gap is defensible.

Parking or storage. Deeded parking spaces and storage units often carry a separate assessed value. Confirm whether your comparables have the same parking situation.

Floor level premium. Many assessors apply a floor-level adjustment. If you're on the 18th floor and your comparables are on the 8th, the assessor may have applied that adjustment correctly. Compare units within two or three floors of your own to neutralize this.

If none of these apply and the gap still exists, proceed with the appeal. The burden is on the assessor, not you, to explain an unexplained differential once you've established the comparison.

How do you document the comparison for your appeal filing?

Your documentation package needs to do one thing: make it effortless for a reviewer who has never seen your building to understand the disparity in 90 seconds.

Include:

• A one-page summary table listing each comparable unit, its square footage, assessed value, and assessed value per square foot, with your unit clearly marked.
• A calculation showing median assessed value per square foot for the comparison group and your unit's percentage above that median.
• Printouts or screenshots from the assessor's own public portal showing the assessed values you used. This part matters. You want the board to see that all numbers come from their own system, not a third party.
• A brief note on any physical differences you investigated and ruled out, so the reviewer knows you considered them.

Most appeal forms have a section for "evidence attached" or "comparable properties." Fill that in completely. Assessors and appeal boards can dismiss vague filings, but they can't ignore a table of their own data showing a 20% gap with no explanation.

Keep the narrative short. One paragraph explaining what you found, one paragraph saying there are no physical differences that justify the gap, and a request for equalization to the median of the comparison group. That's the whole argument.

For help organizing this into a form-ready package, a DIY appeal kit from TaxFightBack walks you through the exact table format and supporting evidence checklist, so you keep 100% of any savings without paying a contingency firm.

Make copies of everything before you submit. Some county offices lose paperwork. Some require original signatures on specific forms. Check your county's instructions for whether electronic or mailed filing is required, and note the deadline, which in most states falls between 30 and 90 days after your assessment notice arrives. ^[6]

What if the assessor's portal doesn't show square footage for individual units?

This is a real problem in some jurisdictions, and it's solvable. Square footage for individual condo units can come from several places besides the assessor's portal.

The HOA's governing documents (often called the plat of condominium or the declaration) contain the legal square footage for each unit. This is a recorded document, usually available through your county recorder's office. For buildings built before online records, a visit or a public records request may be needed, but the document exists.

Your mortgage appraisal almost certainly includes floor plan dimensions and square footage. That appraisal is your property.

Listing history on MLS-based sites (Redfin, Zillow) often shows square footage from when units were last sold. This isn't the official record, but it's a useful cross-check.

Building management companies typically keep unit spec sheets. A simple email to your building manager asking for floor plan square footages for units in your tier is often the fastest path.

If you cannot confirm square footage for specific comparable units, you can still make the comparison by assessed value alone without normalizing for square footage, as long as you note in your filing that all units in the comparison group share the same floor plan designation. The assessor's own records show the floor plan or unit type code in many systems, and that code confirms you're comparing like to like.

Does the comparison approach work for co-ops, too?

Co-ops are taxed differently in most states, and that changes the comparison approach. In a co-op, you don't own real property directly. You own shares in a corporation that owns the building. The building is assessed as a whole, and your slice of the tax bill is allocated by the co-op corporation based on your share percentage.

In New York City, co-op buildings are assessed as a single parcel under Class 2 or Class 4 depending on size. Individual unit assessments don't exist the way they do for condominiums. ^[4] So the unit-by-unit comparison doesn't apply to co-ops in New York.

In states where co-op shares are treated as real property interests for tax purposes, or where the jurisdiction assesses individual proprietary lease interests, the comparison approach may work. But this is jurisdiction-specific. Check with your state's department of revenue or department of taxation to confirm how co-op units are assessed before spending time on a unit-by-unit comparison.

For condominium units, which are individually titled real property in every U.S. state, the comparison approach in this article applies directly.

What are the deadlines for filing a condo assessment appeal?

Deadlines vary by state and sometimes by county, and missing one usually means waiting a full year for your next chance. This is where most homeowners lose money through inaction.

A rough map of common deadlines:

State	Typical appeal window
California	60 days from assessment notice, or July 2 to Sept 15 for regular roll [7]
Illinois (Cook County)	30 days from township reassessment notice publication [8]
New York	March 1 (most municipalities); varies by locality [4]
Texas	May 15 or 30 days after notice is mailed, whichever is later [1]
Florida	25 days from TRIM notice (mailed in mid-August) [9]
Georgia	45 days from assessment notice [10]

These are the starting deadlines. Many states allow a second-level appeal to a state board after the local level, with its own deadline. Confirm the current year's deadline with your county assessor's office directly, since dates can shift.

For major metros covered on TaxFightBack: Cook County, Illinois appeal deadlines and Los Angeles County assessment calendar have dedicated guides with current dates.

What happens at the hearing and how do you present the comparison?

Most condo appeal hearings are informal. You sit across a table from one or two people from the assessment review board or the assessor's office. The whole thing often takes 10 to 20 minutes. Some counties now offer virtual hearings.

Lead with your conclusion, not your story. The first sentence out of your mouth should be: "My unit is assessed at $X, which is Y% above the median assessed value per square foot for the same floor plan in my building, based on the assessor's own public records." Then hand them your one-page table.

Let the table do the work. Most reviewers will look at it, verify a few numbers against their own system, and either offer a reduction or ask questions. The questions are usually: Did you consider view differences? What floor are you on? Are there renovations on record?

Answer those directly and specifically. "I'm on the 12th floor, and the units I'm comparing are on floors 10 through 14. No permits on file for interior renovations. All units face the interior courtyard."

If the reviewer says your unit was flagged for a specific reason, that's useful information even if you don't win. Ask for it in writing. If the reason is incorrect (wrong square footage in the file, wrong unit type code), that's a factual error you can correct on the spot or in a follow-up filing.

If you don't get the reduction you wanted at the informal level, ask about the next step. Most states have a formal appeal to a review board, a board of equalization, or in some states a state tax court. The comparison table you built works at every level.

How much can you realistically save by winning this type of appeal?

Nobody has clean national data on average condo appeal savings. The closest published figures come from individual county reports.

Cook County, Illinois reported that residential appellants who won their appeals in 2022 received reductions averaging about 14% of their assessed value. ^[8] Given that Cook County assesses at 10% of market value, a 14% reduction in assessed value translates to a real but modest change in the actual tax bill, depending on the tax rate.

In New York City, the NYC Tax Commission reported that residential class applicants received reductions in a meaningful portion of cases, with the average reduction for small residential properties in the 2023 roll around 8-12% of assessed value. ^[11]

Here's a concrete example. Your condo is assessed at $400,000, your county assessment ratio is 100% of market value, and your effective tax rate is 1.2%. You're paying $4,800 a year. A 15% reduction in assessed value saves $720 annually. In a high-tax jurisdiction like New York or New Jersey, where effective rates can exceed 2%, the same reduction saves $1,200 or more per year. And savings compound: a lower base assessment this year is your starting point next year.

The cost of a DIY appeal is basically your time. Contingency firms typically charge 25% to 40% of the first year's tax savings. On a $720 saving, that's $180 to $288 gone to the firm. TaxFightBack's appeal kit is a one-time cost that you keep using, and every dollar of savings stays with you.

For context on what's at stake in specific high-value condo markets, see our guides on NYC property tax and Santa Clara property tax.

What if every unit in the building seems over-assessed, more than yours?

This happens, especially after a reassessment year. If every comparable unit in the building is assessed at what looks like an inflated level, your intra-building comparison won't show a disparity, because the disparity is between the building and the market, not between units.

In that case, you need a market value argument, not an equity argument. The evidence shifts from internal unit data to recent sale prices of similar condo units in comparable buildings nearby. That's a harder case to build, and it usually requires comparable sales analysis along the lines of what an appraiser would produce.

You can still do it yourself. Pull recent condo sales from your county's deed transfer records or from public MLS data (Redfin shows sale history on most listings). Select units in nearby buildings of similar vintage, construction type, and amenity level. Calculate price per square foot at sale and compare to your building's assessed value per square foot. If the building as a whole is assessed above recent market sales, that's your argument.

In some states, you can combine both arguments in one filing: the building is assessed above market, and my unit is assessed above the building's own median. That's a stronger filing because it gives the board two independent paths to grant you a reduction.

If your county is in a major metro, check our local guides for jurisdiction-specific advice: Montgomery County property tax, Hennepin County property tax, and Gwinnett County tax assessor all cover local appeal standards.

Frequently asked questions

Can I appeal my condo assessment based on a neighbor's lower assessment for an identical unit?

Yes, and it's one of the cleaner arguments in property tax appeals. You don't need a single neighbor with a lower value. Gather the assessed values for all units with the same floor plan in your building, calculate the median, and show that your unit sits materially above it. Most state assessment laws require uniform treatment of similar properties, so a documented gap with no physical explanation is a valid basis for appeal.

How do I find out what my neighbors' condos are assessed at?

Assessment records are public in every U.S. state. Go to your county assessor's website and search by the building's street address. Most portals return all parcels at that address, each with its assessed value. If the portal is limited, submit a public records request to the assessor's office for all parcel assessments at your building's address. The data is free and must be provided.

What if my unit has upgrades that the comparable units don't have?

Check whether those upgrades were permitted. Permitted renovations can appear in the assessor's file and legitimately increase your assessed value. Unpermitted work generally won't be reflected. If comparable units also have unpermitted renovations that the assessor is unaware of, the comparison still holds. If your unit genuinely has superior finishes documented in the assessor's record, a smaller gap may be defensible.

Does floor level affect whether two condo units are comparable for an appeal?

Yes. Assessors often apply a floor-level adjustment, giving higher floors a premium. To keep your comparison clean, restrict your comparable group to units within two or three floors of your own. If you're on the 10th floor, compare to units on floors 8 through 12 with the same floor plan. That neutralizes the floor premium as a counterargument and keeps your comparison group credible.

How long does a condo assessment appeal typically take?

At the informal or administrative level, most counties schedule hearings within 30 to 90 days of your filing, and decisions come within a few weeks after that. If you proceed to a formal board of equalization or tax court, the timeline stretches to 6 to 18 months in many jurisdictions. Texas informal hearings often resolve in the same season. Cook County, Illinois formal appeals can take 12 to 24 months.

What is an unequal appraisal protest, and how is it different from a market value protest?

A market value protest argues that the assessor's estimate of your condo's market value is too high. An unequal appraisal protest argues that even if the value were correct, your unit is assessed at a higher ratio than comparable units. Texas Tax Code Section 41.43 allows both arguments in the same filing. The unequal appraisal argument uses only the assessor's own data, making it easier to prove without hiring an appraiser.

Can I use Zillow or Redfin data to compare condo assessments?

Not for the intra-building equity argument. You want the assessor's own assessment data, not market value estimates. Zillow and Redfin help when you argue that your building as a whole is over-assessed relative to market value, where you'd compare recent sale prices of similar condo units nearby. For the unit-by-unit equity comparison, stick to the assessor's public records.

What if my county assessor's website is hard to use or doesn't show all units?

Submit a public records request (called a FOIA request at the federal level; states have equivalents) to the assessor's office asking for all parcel assessments at your building's address. This is a routine request that assessor offices handle regularly. Many counties also publish downloadable assessment roll files you can filter by address. Ask the assessor's public counter directly; they often have a shortcut that saves you hours.

How many comparable units do I need for a strong equity argument?

More is better, but even 4 to 6 solid comparables can support a strong filing. What matters is that the comparables share your floor plan, sit in the same building, and lack physical differences that justify a gap. If your building has 20 units of your floor plan, include all 20. A larger sample makes it harder for the assessor to pick apart the comparison.

Will winning an appeal based on other units' assessments cause those units to be reassessed upward?

In most states, a successful appeal lowers your assessment only. It does not trigger a reassessment of the comparable units you used. However, the information you submit becomes part of the public record, and in theory an assessor could review comparable units afterward. In practice this rarely happens. Your filing improves your own situation; what the assessor does with the rest of the building is independent of your appeal.

Can I appeal a condo assessment in a newly constructed building where there are no prior sales?

Yes, and the intra-building comparison is especially useful here because sale comparables from outside the building may be sparse. If the developer sold identical units at different prices, those deed transfer prices are public record and can also support a market value argument. The equity argument comparing unit to unit works well when the assessor's model applied inconsistent values across the same floor plan in a new building.

Is there a filing fee to appeal a condo property tax assessment?

Most jurisdictions have no filing fee for the first level of appeal (the informal hearing or administrative review). Some states charge a modest fee, typically $25 to $75, for formal appeals to a board of equalization or review. State tax court appeals can carry higher filing fees, sometimes $100 to $200 or more. Check your specific county's appeal instructions. The fee, where it exists, is almost always less than one month of potential savings.

What if my HOA is involved in a building-wide assessment dispute?

Some HOAs file blanket appeals on behalf of all units, especially in states like Florida where the building's common areas and land are assessed at the HOA level. Even if your HOA is appealing, you may still have the right to file an individual unit appeal. Check with your HOA board and confirm with your county whether individual and HOA appeals can run concurrently. Don't assume the HOA's appeal covers your unit's individual assessed value.

What should I do if the assessor says my condo's value is based on a sales study, not individual unit comparisons?

Ask for the sales study and the specific comparable sales used. Mass appraisal models are built on samples, and if the sample missed your building or used dissimilar properties, that's an argument for review. You can also counter with your intra-building data: regardless of the market study, the model produced an inconsistent result within the same building, which is an equity violation independent of whether the model's market value estimate was reasonable.

Sources

1. Texas Legislature, Texas Tax Code Section 41.43: Texas Tax Code Section 41.43 allows an unequal appraisal protest if the assessed value exceeds the median level of appraisal of comparable properties, and the appeal deadline is May 15 or 30 days after notice, whichever is later.
2. Cook County Assessor's Office, Assessment Roll and Appeal Information: Cook County publishes its full assessment roll publicly and groups condominium units by class code; residential appellants who won appeals in 2022 received reductions averaging about 14% of assessed value.
3. Los Angeles County Assessor, Property Search Portal: The Los Angeles County Assessor portal allows address-based searches that return all parcels at a given address, including individual condo units.
4. New York City Department of Finance, Property Tax and Assessment Information: New York City assesses co-op buildings as a single parcel; individual condo unit assessment data is publicly searchable by address; appeal deadline for most properties is March 1.
5. International Association of Assessing Officers (IAAO), Standard on Ratio Studies: IAAO standards specify that the coefficient of dispersion for residential assessment uniformity should be 15% or less.
6. Lincoln Institute of Land Policy, Significant Features of the Property Tax: Property tax appeal windows in most states range from 30 to 90 days after the assessment notice is mailed.
7. California State Board of Equalization, Assessment Appeals Overview: California's regular assessment appeal period runs July 2 through September 15; for notices mailed outside that window, the window is 60 days from the notice date.
8. Cook County Assessor's Office, Annual Report 2022: Cook County township reassessment notices trigger a 30-day appeal window from the date of publication.
9. Florida Department of Revenue, Property Tax Oversight, Assessment Appeals: Florida's appeal deadline is 25 days from the TRIM (Truth in Millage) notice, which is typically mailed in mid-August.
10. Georgia Department of Revenue, Property Tax Appeal Information: Georgia property owners have 45 days from the date of the assessment notice to file an appeal.
11. NYC Tax Commission, 2023 Annual Report: NYC Tax Commission reported average assessment reductions of approximately 8-12% of assessed value for residential class applicants in the 2023 assessment roll.