Nassau status: The 2028/29 window is currently open. Final extended deadline is March 31, 2027.
Suffolk status: The 2026/27 window closed May 19, 2026. The next deadline is May 18, 2027.
Side-by-side: Nassau vs. Suffolk
| Nassau County | Suffolk County | |
|---|---|---|
| Current tax cycle being grieved | 2028/29 | 2026/27 |
| Statutory deadline | March 1, 2027 | May 19, 2026 |
| Extended deadline (if any) | March 31, 2027 | — (no extension) |
| Filing opens | January 2027 | 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, 2028 | Town BAR notice ~July |
| First bill that reflects reduction | October 2028 | December 2026 |
Nassau filing window
Nassau’s grievance window opens January 2 each year. The statutory deadline is March 1, 2027, but the Assessment Review Commission has consistently extended it to March 31, 2027 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 2028/29 tax cycle — that’s the school tax bill that arrives October 2027 and the general tax bill that arrives January 2028. ARC has until March 31, 2028 to resolve every filing.
Suffolk filing window
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).
Frequently asked questions
Can I file in both counties if I own property in both?
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).
What’s the difference between the statutory and extended Nassau deadline?
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, 2027. Treat the statutory date as your safe target — only rely on the extension if it’s officially announced for the current cycle.
How do I know if my deadline was extended?
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.
If I miss the deadline, is there any way to still grieve?
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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Sources and citations
- NY Tax & Finance — Contest your assessment tax.ny.gov
- Nassau County Assessment Review Commission nassaucountyny.gov
- Suffolk County Comptroller — Information for taxpayers suffolkcountyny.gov
- Suffolk County Clerk — Small Claims Assessment Review suffolkcountyny.gov
- JDSupra — 2026 Suffolk grievance filing period jdsupra.com
- Farrell Fritz — Nassau extends 2027/28 grievance deadline to Mar 31, 2026 farrellfritz.com
Last verified October 8, 2026. Tax rules change; we re-check every page each quarter.
Educational content and estimates only, not legal, tax or financial advice. Verify with your county or town receiver, an attorney or a CPA before making financial decisions.