Your annual bill is the sum of every taxing district that overlaps your parcel — typically school + county + town + library + fire + sewer + sometimes a village. Each district levies its own millage rate against your assessed value. Here's exactly how that math works, step by step.
The one-line formula: Your annual property tax = (your home's assessed value ÷ 1,000) × (combined millage rate) − exemptions. Each piece below explains how that calculation actually gets to a specific dollar bill.
The county assessor maintains an assessed value (AV) for every parcel. This is NOT the market value — it's a derived number that depends on each county's assessment methodology:
To find your assessed value: it's on your tax bill, on the assessment roll, and on our calculator when you look up your address.
Millage is "tax per $1,000 of assessed value." A typical Long Island parcel is in 5-9 overlapping taxing districts, each with its own millage:
You add all the millages together to get a combined millage rate. The Department of Assessment publishes per-district millage every year as part of the tax warrant. The calculator reads all of these from public NY State data.
Annual tax (before exemptions) = (AV ÷ 1,000) × combined millage.
Worked example, single-family home in Suffolk (Sachem school district, Town of Brookhaven):
Worked example, Nassau home (East Meadow school district, Town of Hempstead):
Same-ish bill, totally different "rate" — because Nassau's LoA is 9x smaller than Suffolk's, Nassau's millage has to be 9x bigger to produce the same dollar tax. This is why comparing millage rates between counties (or even between Suffolk towns) is meaningless. Compare effective rate instead.
If you qualify for exemptions, they reduce either the assessed value (exemption form) or the bill itself (credit form). The most common LI exemptions:
See: STAR explained, Senior, Veterans, Disabled.
Skip the math: Type your address into the calculator and it does every step automatically against 847,826 indexed LI parcels. It pulls your assessed value, every district's millage, and applies exemptions — then shows the bill and the breakdown.
The assessed value is intentionally not market value — it's scaled by the Level of Assessment (LoA), which is a per-municipality constant. Nassau's LoA is 0.10%, meaning the AV is 1/1000th of market value. Suffolk LoAs vary by town but are generally under 1%. The "real" assessed-to-market ratio for residential properties is called the Residential Assessment Ratio (RAR), and NY State publishes it annually for every municipality.
Because Nassau's LoA is 9-10x smaller than Suffolk's. To raise the same dollar tax, you either multiply a big AV by a small rate, or a small AV by a big rate. Nassau picked the small-AV, big-rate route. Suffolk towns picked the bigger-AV, smaller-rate route. Either way the resulting dollar bill is what matters. Effective rate (bill / market value) is the only fair comparison.
NY has a 2% property tax cap (§2022 of NY Tax Law) that limits the year-over-year growth of the tax LEVY (the total dollars a district collects), not individual bills. Districts can pierce the cap with a 60% override vote. Within that limit, the millage is set to whatever produces the levy when multiplied by the assessment base. So if assessments go UP, millage usually goes DOWN to keep the total levy under cap. Individual bills can still move ±5-15% depending on how your specific assessment changed vs. the district average.
One annual bill, but split into halves. Nassau bills school in Oct/Apr and general in Jan/Jul. Suffolk towns send one bill in December covering Dec/May halves. Full payment schedule.
Grievance deadlines, STAR limit updates, new exemption laws. One short email, only when something actionable happens. Unsubscribe in one click.
Subscribe →Last verified: 2026-05-23. Tax rules change; we re-verify each page quarterly.
Estimates and educational content only — not legal, tax, or financial advice. Verify with your county or town receiver, an attorney, or a CPA before making financial decisions.