Why this changes the grievance strategy, not just the outcome

This is the practical consequence for a board. The two classes are valued by different methods, so they are challenged with different evidence.

A Class 1 condominium is valued on comparable sales. The grievance is a sales-comparison argument: what did comparable units actually trade for, and is the assessor's figure out of line?

A Class 2 condominium is valued as if it were a rental building. The grievance is an income-capitalisation argument: what rent would this building actually produce, what are the operating expenses, and what capitalisation rate applies?

A board that files a sales-comparison grievance on a Class 2 building is answering a question the assessor did not ask. And a board in a converted building is structurally worse off — no cap, income-based valuation — which is an argument for filing every year rather than only when an increase is noticed.

The dates, and be careful which roll they belong to

The grievance window for the current cycle, per the Town of Hempstead's assessment page: “January 2, 2026, through March 31, 2026,” with mailed applications “postmarked by March 31, 2026.”² Nassau County's own frequently-asked-questions page states the filing deadline for assessment appeals as “March 1, 2027” — which is a different roll.

Both are quoted as the county and town published them. They refer to different assessment rolls, and a board needs to know which roll it is challenging before it relies on either date.

Useful mechanics: the Assessment Review Commission “can keep a Tentative Assessed Value unchanged or lower an assessment, but it cannot raise the assessment” — so a grievance carries no downside risk of a higher number. A Small Claims Assessment Review petition costs $30, filed in the County Clerk's Office. Filing channels include the county's online system, by phone, in person at 240 Old Country Road in Mineola, or by mail.

The larger risk sits with a town board vote, not with the assessor

Real Property Tax Law § 581 caps a condominium's assessment at what the parcel would carry if it were not in condominium form. That is the protection every New York condominium relies on, and it has an off switch.

A municipal corporation may adopt a local law switching the § 581 limitation off for converted condominium units. The mechanism, as we understand it, requires the local law to be adopted before the taxable status date of the roll it is to affect — which for most New York towns is March 1.

We have to be careful here, and we are going to be. We could not open a primary source for § 581's text — the hosts carrying New York's codified municipal and tax law refused every request from this environment — so we are describing the mechanism as reported rather than quoting the statute. We also could not verify a single 2025 or 2026 adoption of such an opt-out anywhere in New York. Search results identified pre-existing opt-outs in the Town of Clarkstown and Village of Piermont in Rockland County and the Town of Amherst in Erie County; none is verified and none is dated 2025 or 2026.

What that warrants is not alarm but attention. If a town adopts the opt-out, converted condominium units in that town lose the § 581 ceiling and get assessed like any other parcel — typically a substantial, permanent increase in every owner's tax bill, arriving without any change to the property. It is decided by a town board vote before a March taxable status date, usually with minimal notice. For a board in a converted building, the town board agenda is the only warning.

One related state bill, as a lead rather than a finding: S3213 (Kavanagh) would add a subdivision to § 581 clarifying that current law does not require co-op or condominium property to be assessed on the income it would generate as a rental. It has never moved — referred to Senate Local Government in January 2025 and re-referred January 2026, with no companion. A separate bill, S619 (Stavisky), on limits on assessed value for parcels held in co-op or condominium form, has the same history.

Three other Nassau County laws that reach owners' bills

From the county's 2026 local laws, three change who qualifies for partial exemptions on a unit — which matters directly in age-restricted and senior condominium and HOA communities, where a board fields these questions constantly:

Local Law 4 of 2026 raises the maximum income eligibility level for the Real Property Tax Law § 467 limited-income exemption. Local Law 5 of 2026 creates a partial exemption for surviving spouses of volunteer firefighters and ambulance workers killed in the line of duty. Local Law 9 of 2026 creates an exemption for veterans rated 100% disabled.³

A board cannot apply for an owner's exemption, but it can tell its members these exist — and in a senior community that is a more valuable communication than most of what a board sends out. Our New York assessment limits page covers the assessment framework and our budget approval page covers the association side of the same household bill.