Two different counties, two different deadlines. Nassau's window closes March 31, 2026 (extended from the statutory March 1, 2026). Suffolk's window closes Tuesday, May 19, 2026. Missing either one means waiting a full year for the next chance.
Nassau status: The 2027/28 window closed March 31, 2026. The next window opens January 2027.
Suffolk status: The 2026/27 window closed May 19, 2026. The next deadline is May 18, 2027.
| Nassau County | Suffolk County | |
|---|---|---|
| Current tax cycle being grieved | 2027/28 | 2026/27 |
| Statutory deadline | March 1, 2026 | May 19, 2026 |
| Extended deadline (if any) | March 31, 2026 | — (no extension) |
| Filing opens | January 2026 | May 1, 2026 |
| Where you file | Nassau Assessment Review Commission (ARC) — online | Your town's Board of Assessment Review (BAR) |
| Filing fee | $0 (DIY) or % contingency (firm) | $0 (DIY) or % contingency (firm) |
| Resolution by | March 31, 2027 | Town BAR notice ~July |
| First bill that reflects reduction | October 2026 | December 2026 |
Nassau's grievance window opens January 2 each year. The statutory deadline is March 1, 2026, but the Assessment Review Commission has consistently extended it to March 31, 2026 in recent years. The extension is announced by ARC; you should treat the statutory date as the safe deadline and only count on the extension if it's been formally announced for the current cycle.
Filing is done through ARC's online portal (no paper required). You're grieving the 2027/28 tax cycle — that's the school tax bill that arrives October 2026 and the general tax bill that arrives January 2027. ARC has until March 31, 2027 to resolve every filing.
Suffolk's window is much shorter: 13 business days from May 1 to the third Tuesday of May. For the 2026/27 cycle, the deadline is Tuesday, May 19, 2026. There is no extension — the third-Tuesday date is set by state statute (RPTL §512) and Suffolk does not extend it.
You file with your town's Board of Assessment Review, not the county. That means there are 10 separate town filing offices in Suffolk; the deadline is the same for all of them but the office address and submission method varies by town. Notice of the BAR decision typically arrives in early-mid July. If denied, you can escalate to Small Claims Assessment Review (SCAR) within 30 days for a $30 filing fee.
Missed the deadline? Your only real option is to wait for the next cycle. There is no late-filing process — boards cannot accept a complaint after the deadline. Read what happens if you missed Suffolk's deadline for the workarounds (which are mostly: prepare for next year).
Yes. The filings are completely independent — you file separately for each parcel with the relevant county/town. The deadlines, forms, and processes are different (Nassau ARC online vs. Suffolk town BAR).
Statutory means written into NY State law (March 1). Extended means ARC has formally announced an extension under their authority. The recent extended deadline is March 31, 2026. Treat the statutory date as your safe target — only rely on the extension if it's officially announced for the current cycle.
Nassau: check the ARC website for current-year announcements. Suffolk: there is no extension — the third-Tuesday-of-May date is fixed by statute and cannot be extended.
Not for the cycle that already closed. You'll have to wait for the next opening. In the meantime: track recent comparable sales, photograph any condition issues, and prep your case so you can file the moment the next window opens. See missed-deadline workarounds.
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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.