New York has no primary-residence registry. Here is what co-op and condo owners must do about the pied-à-terre notice before September 18.

New York Tax Law Article 30-C, effective July 1, 2026, imposes an annual surcharge on non-primary residences above specific market-value thresholds: $1 million for co-op units and condominium apartments, $5 million for one-to-three-family homes. The Department of Finance published 959,710 property records on its July 24 supplemental market-value roll and mailed approximately 17,000 letters. If you received one of those letters, or if you manage a co-op building where a shareholder received one, the deadline to prove primary residence is September 18, 2026.

What the notice says, and what it does not.

The DOF notices carry the phrase "You may be subject to the pied-à-terre surcharge." That language is specific: it activates the window to prove primary residence. It does not mean you owe the surcharge. It means DOF's records place your unit above the market-value threshold and do not confirm you as a primary resident from the data sources DOF used to screen the roll.

DOF identified potential pieds-à-terre by screening against existing exemptions and abatements: co-op and condo abatement enrollment, NYC resident income tax filings, STAR (School Tax Relief) participation, and similar residency proxies. Properties that did not appear on those lists, or appeared on lists that did not fully resolve primary-residence status, landed on the supplemental roll. A condo unit in a building that opted out of the abatement, for example, lacks the abatement record as a positive signal. Without that signal, DOF had no basis to exclude the unit.

The letter contains a personalized PIN and a web link to the DOF filing portal at nyc.gov/npsurcharge. The portal is the only accepted filing channel under DOF's final rules. Paper submissions are not accepted.

New York has no primary-residence registry.

That is the structural fact underneath what officials described as a "confusing rollout." Other states and cities maintain centralized databases that confirm primary residence: homestead exemption registries, state income tax residency flags tied to address records, voter registration files cross-referenced against assessment records. New York City has none of these tied to a single authoritative registry that DOF can query to confirm who lives where year-round.

Tax Law Article 30-C, adopted as Part HH of the 2026-2027 State Budget, requires DOF to make annual primary-residence determinations. The department built a screening methodology from proxy data: abatements, exemptions, and tax filings that correlate with primary residency. The proxy approach works when the proxies are complete. When they are not, as with buildings outside the abatement or owners who file taxes jointly at a different address, the proxy underidentifies primary residents, and those owners land on the roll.

The result is an opt-out structure. A co-op or condo owner with a unit valued above the threshold is presumed to be a non-primary resident unless DOF's proxies flag otherwise. The burden of proof runs to the owner. The September 18 extension exists, by the Mayor's own characterization, because the opt-out window at the original pace produced more confusion than the city could process. DOF acknowledged receiving thousands of exemption inquiries before the first set of letters had finished mailing.

This pattern is not new. The co-op and condo abatement (RPTL §467-a, now expired) required annual primary-residence certification for the same reason: DOF could not determine who lived where without asking. The STAR exemption requires the same certification annually. The pied-à-terre surcharge adds a third layer to the same absence. Each time the city or state creates a primary-residence-based benefit or obligation, it recreates the same mechanism from scratch rather than building a shared infrastructure.

The co-op board's coordination problem.

For co-op shareholders, the surcharge creates a specific board-level coordination gap. Under Tax Law Article 30-C, DOF bills the surcharge to the co-op corporation as a single item on the building's property tax bill. The corporation collects it from shareholders who are subject. But the exemption application is filed by the individual shareholder, not by the board.

That split means the board must take four steps that no state law requires it to take:

• Identify which shareholders received a DOF notice, or determine which units DOF has flagged as potentially subject based on the supplemental roll.
• Communicate the September 18 deadline and the required documentation to each affected shareholder before that window closes.
• Establish a collection mechanism for any shareholders who are actually subject and do not file an exemption, so the building is not left absorbing the surcharge on their behalf.
• Understand that a shareholder who misses September 18 may be billed as a non-primary resident for tax year 2026-27, even if they do in fact live in the unit full-time.

Most of this coordination runs through the managing agent, who typically sends building-wide communications and tracks DOF notices on behalf of the board. That managing agent needs no state license in New York. S.71, the managing-agent registration bill, has not received a committee hearing in ten consecutive sessions.

Documents that satisfy DOF.

Under DOF's final rules adopted July 14, 2026, all submissions go through the personalized PIN and portal in the notice letter. If you did not receive a letter but believe your unit appeared on the supplemental roll, DOF has a separate inquiry channel at the same portal. Owners who did receive a letter and do not file by September 18 will be treated as non-primary residents for the 2026-27 and 2027-28 tax years, subject to any subsequent appeals.

What pending legal challenges mean for your deadline.

Multiple lawsuits challenge Tax Law Article 30-C on constitutional grounds, including equal-protection and property-tax-uniformity arguments. None of the pending litigation suspends the September 18 filing requirement. DOF confirmed that challenge proceedings under the State Administrative Procedure Act do not toll the exemption application window. If you are a primary resident and miss the September 18 deadline, your administrative path to a $0 surcharge for 2026-27 is foreclosed regardless of how the litigation resolves.

The financial stakes are not abstract. The surcharge for a co-op or condo unit at the $1 million DOF market value floor is approximately $40,000 annually — 4 percent applied to the full DOF market value, not just the excess above threshold. Units above $3 million enter the 5.25 percent bracket, giving a minimum annual bill of approximately $157,500. Missing the administrative window to prove primary residence costs a primary resident several years of surcharge exposure before any judicial relief could arrive. File first.

What comes after September 18.

The September 18 window is for the 2026-27 and 2027-28 tax years. DOF has stated it will run the same proxy screening annually. That means the opt-out cycle repeats each year: DOF screens the roll using proxies, identifies units that lack a positive primary-residence signal, sends notices to those units, and relies on self-identification by owners to clear the field.

Owners whose proxies do not align with their actual primary residence, because their abatement enrollment lapsed, their income tax return lists a different address, or their building opted out of the abatement, will receive notices in future years unless their proxy record is corrected. For co-op boards, this means the September coordination problem is not a one-time event. It is an annual administrative cycle with no state law requiring the board to run it.

Bottom line.

Tax Law Article 30-C targeted roughly 13,000 pieds-à-terre and drew 959,710 properties into the DOF screening roll because New York has no mechanism for confirming primary residence except by asking owners to prove it. The September 18 extension is an acknowledgment that the opt-out pace the statute assumed was not achievable. For primary-resident co-op and condo owners who received a notice: gather your most recent tax return, or a NY driver's license plus a supporting document, and file at nyc.gov/npsurcharge before September 18. For co-op boards: identify which shareholders received notices and send the deadline and documentation requirements to them now. Missing the window does not resolve the underlying absence. DOF will screen the roll again in 2027, and the September cycle will repeat.

Primary sources: NY Tax Law Article 30-C §§1350–1356 (Part HH, Chapter 59 of the Laws of 2026) · NYC Mayor's Office and DOF Commissioner Lee, press release, August 1, 2026 (extending deadline to September 18) · Greenberg Traurig, “NYC DOF Finalizes Rules and Begins Exemption Review Process,” August 2026 · National Law Review, “NYC DOF Finalizes Rules and Sends Notices,” 2026 · Katten Muchin Rosenman, “Received a NYC Pied-à-Terre Tax Notice?” 2026

Companion resources: Taxed as a rental building: why 959,710 properties appeared on the DOF roll · One shareholder's unpaid surcharge can lien your entire co-op · How co-op boards collect the pied-à-terre surcharge from shareholders · How co-op boards became state tax collectors · Issue: no mandatory financial disclosure to buyers