Understanding Your Property Assessment

The county assesses your property every year. Reviewing and understanding your assessment notice early can make all the difference in your tax bill before the March 2 grievance filing deadline. The assessed value is Nassau County’s estimate of your property’s market value – what the county believes your home would sell for on the open market – which is a percentage that is used to calculate your property taxes. The market value is multiplied by the level of assessment to produce your assessed value. Then your assessed value is multiplied by the local tax rates, which are set by the county, school district, and other taxing authorities, to determine the property tax you owe. Essentially, your assessed value is the foundation of your property tax bill. So, if your assessed value increases, even if tax rates stay the same, your property tax bill will likely increase.

The county’s estimate of the market value may not reflect true home sale prices. Common reasons assessments are too high could be due to outdated data, neighborhood variations, or overgeneralized modeling. If your assessment is higher than your home’s true market value, you may be overpaying in taxes, and that’s where filing a grievance by the March 2 deadline can help correct the overassessment and lower your bill.

Step-By-Step Example

In Nassau County, property taxes are calculated using the Residential Assessment Ratio (RAR), which is determined by the local municipalities within Nassau County. Now let’s look at a step-by-step example:

Let’s say your home’s market value is estimated by the county at $800,000 and the RAR of your property is 0.10% (0.001 as a decimal) to calculate assessed value.

Step 1: Calculate Assessed Value

$800,000 x 0.001 = $800

Your assessed value is $800.

Step 2: Apply Local Tax Rates

Your total local tax rate might total 1,200 per assessed dollar.

$800 x 1,200 = $960,000

Since tax rates are expressed per $100 of assessed value in Nassau County, that results in:

($800/100) x 1,200 = $9,600

Estimated annual property tax: $9,600

How the Grievance Process Affects Your Tax Bill

It is important to note that filing a grievance (also known as an appeal) does not delay your property tax payments, but if your grievance is approved, the lower assessment will reduce your future tax bills. If you have already started paying, in some cases, overpayments may be refunded or credited toward future taxes.

Since assessments form the basis for your property taxes, even a modest reduction in assessed value can save hundreds or thousands annually over multiple years. Vice versa, even a slight increase in your assessed value can lead to savings in higher taxes each year. The only time a higher assessment might not increase your tax bills is if your assessment rose less than the average increase across the county, but in Nassau that is uncommon for many residential properties.

That’s why reviewing and appealing your assessment is so important when Nassau County releases the 2026 values on January 2. Reducing your assessment through a successful grievance doesn’t just save you once but can deliver savings year after year, one of the smartest financial moves you can make.

How to File a Grievance

The following are four key steps to follow when filing a grievance on your own:

• Step 1 Check your assessment:Make sure to visit the Nassau County Department of Assessment site to access your 2026 tentative assessment once it’s published January 2.
• Step 2 Compare market value:Confirm whether your assessed market value aligns with recent sale prices by comparing similar homes in your neighborhood.
• Step 3 File your grievance: File a grievance through the Assessment Review Commission (ARC) online between January 2 and March 1, 2026. No attorney or representative is required, but accuracy and evidence are key for this step.
• Step 4 ARC’s determination: Track your case and wait for the ARC’s determination. The county reviews all filings and often issues decisions later in the year. If you are successful, your assessment and hopefully your future tax bill will be reduced.

Why Professional Help Can Pay Off

Property owners can encounter stressors and possible obstacles when filing a tax grievance on their own. The appeal process can be tricky because it is data-driven, uses comparable sales analysis, involves legal understanding, and valuation models. Having a clear understanding of these practices and concepts can significantly impact the outcome of your appeal. O’Connor property tax specialists handle the filings, evidence, and follow-ups for you, so you don’t have to take on the added stress. O’Connor has access to comprehensive market data including recent sale prices of comparable homes and neighborhood trends, providing an effective way to gather evidence for grievances. We also have access to advanced real estate databases and valuation tools beyond what is publicly available. We have the tools necessary to present a compelling, data-backed argument when a property’s market value and assessment is too high.

Stay Ahead of the 2026 Grievance Season

Filing a grievance on your own is possible, but professional representation can increase your odds of success, save you time, and ensure you have more money in your pocket. The appeal window between January 2 through March 1 can quickly come and go before you even realize it. Enroll early before the January 2, 2026, opening date and work with O’Connor. With us, you’ll get automated filing, no missed deadlines, a stress-free process, and performance-based fees. Act early by reviewing your assessment and partner with us for professional help and results that speak for themselves. We offer residential property tax reduction services not only in Nassau County, but also in Suffolk and Westchester counties. With expertise in local valuations and assessment rules, we have a track record of successful reductions for homeowners across New York. Don’t wait for your tax bill to surprise you and start your appeal strategy today.