What the notice number is—and is not
The DOF surcharge letter assigns each property a notice number. That identifier is required when filing an exemption application or appealing the determination, and DOF correspondence will reference it throughout the process.
The number itself is not a calculation. Professional sources and DOF materials establish that the notice number is a case identifier, nothing more. It does not encode the property's market value, surcharge tier, borough, or tax class in a publicly documented format.
Owners searching for their exposure should look elsewhere in the letter. The valuation base—the figure that determines whether the surcharge applies and at what rate—is the DOF phase-one market value, drawn from the department's July 2026 supplemental market value roll and printed separately in the assessment materials.
Where the market value appears, and why it matters
For condominiums and cooperatives, the surcharge is calculated on market value, not assessed value. DOF's final rules, adopted under 19 RCNY chapter 62, state that 'the surcharge is based on market value, not assessed value' and that phase-one market values are 'DOF market values calculated for real property tax purposes.'
That distinction matters. Assessed value for Class 2 properties runs roughly 45 percent of market value and is used only for the regular property-tax calculation. The surcharge uses the full market figure.
The rate structure is flat, not marginal. Once a condominium or cooperative unit crosses $1 million in market value, the applicable rate—4 percent for $1 million through $3 million, 5.25 percent for more than $3 million through $5 million, and 6.5 percent for market value above $5 million—applies to the entire valuation, as established in Tax Law section 1353 and DOF's final rules.
A unit valued at $5.1 million owes 6.5 percent of $5.1 million, or $331,500 annually, if it is determined to be a non-primary residence. A unit at $4.9 million owes 5.25 percent of $4.9 million, or $257,250. The $200,000 difference in valuation produces a $74,250 swing in the annual bill.
The deadline printed on the notice is not the deadline that governs
DOF originally set an exemption-application deadline of August 21, 2026, for one-, two-, and three-family homes and condominium units, and August 24 for cooperative units. The department extended that deadline to September 18, then to October 6.
On October 6, 2026, DOF extended the deadline a third time to October 13, 2026. That is the operative date for all owners who received a 'you may be subject to' notice, regardless of what earlier date is printed on the letter itself.
Owners who miss October 13 may still challenge the determination by filing a TC107 application with the New York City Tax Commission. For properties in Tax Class 2—the category that includes most condominiums and cooperatives—the Tax Commission deadline is March 1, 2027. For Tax Class 1 properties appealing both the primary-residence finding and the market-value determination, the deadline is March 15, 2027.
The Tax Commission route does not replace the DOF exemption process; it is a separate appeal mechanism with its own procedural requirements and later deadlines.
One owner's arithmetic, and what to check now
A cooperative owner in zip code 10019 received a notice in late August showing a market value of $3.2 million. The letter referenced the September 18 deadline, which had already been superseded. The owner's unit falls in the $3 million-to-$5 million band, triggering a 5.25 percent rate on the full $3.2 million—$168,000 annually—if DOF's non-primary determination stands.
The owner's adult daughter lived in the unit for eleven months of 2025 and holds no other New York residence. Under the statute's immediate-family exemption, occupancy by a child qualifies the unit as primary. The owner filed supporting documentation with DOF on October 10, three days before the final deadline.
If the exemption is granted, the $168,000 liability disappears. If DOF denies it, the owner may appeal to the Tax Commission by March 1, 2027, and the first payment—due January 1, 2027, under the statute—will come due while that appeal is pending.
Conquest's analysis of DOF's July 2026 supplemental market value roll shows 16,709 Manhattan condominium and cooperative units with market values above $1 million. Zip code 10019 alone accounts for 975 of them. The median surcharge for units in that zip, if all were determined non-primary, would be roughly $53,000.
Most of those units are primary residences and will owe nothing. The October 13 deadline applies to every owner who received a notice, and the penalty for missing it without a subsequent successful Tax Commission appeal is the full annual surcharge plus a potential 50 percent penalty on late filings.
Our free DOF market-value and surcharge calculator pulls your property's valuation directly from the July 2026 roll and shows the exposure under each rate band. It does not replace the notice, but it confirms the figure DOF is working from and the bracket that applies if the non-primary determination is upheld.
Frequently asked questions
Is my apartment subject to the surcharge based on assessed value or market value?
The surcharge is calculated on market value, not assessed value. DOF's final rules state that the surcharge is based on market value, specifically the phase-one market values calculated for real property tax purposes, which for Class 2 properties is significantly higher than the assessed value used for regular property tax.
How much is the tax on a $5 million apartment under the pied-à-terre surcharge?
A unit valued at $5.1 million owes 6.5 percent of the entire $5.1 million, which equals $331,500 annually, if it is determined to be a non-primary residence. The rate structure is flat, not marginal, so once a unit crosses into a bracket, that rate applies to the full valuation.
Does the ruling change if my adult child lives in the apartment full-time?
Under the statute's immediate-family exemption, occupancy by a child qualifies the unit as primary residence. If your adult daughter lived in the unit for eleven months of 2025 and holds no other New York residence, the unit may qualify for exemption and the surcharge liability would disappear if DOF grants the exemption.