The BBL System: NYC's Property DNA
Every property in New York City carries a unique identifier called a BBL — borough-block-lot — that serves as the Department of Finance's primary key for tax records and the new pied-à-terre surcharge.
The borough code runs 1 through 5: Manhattan (1), the Bronx (2), Brooklyn (3), Queens (4), and Staten Island (5). The block identifies the tax block within that borough. The lot identifies the specific tax lot within that block.
For a brownstone at 123 East 78th Street, the BBL might read 1-1234-56, meaning Manhattan, block 1234, lot 56. This identifier appears on property tax bills, DOF notices, and the surcharge roll that determines who owes NYC's new non-primary residence tax.
Why the Surcharge Roll Keys to BBL
The pied-à-terre tax, effective July 1, 2026, assesses surcharges against specific DOF property records, not street addresses or apartment numbers.
Conquest's analysis of DOF's July 2026 Supplemental Market Value Roll shows roughly 24,000 units citywide would owe the surcharge if the units qualify as non-primary residences. Manhattan condos and co-ops account for roughly 16,700 of those units, with potential surcharges averaging $68,559.
The tax applies flat rates to full market values once properties cross the $1 million threshold for condos and co-ops. A $1.5 million condo would face a 4% surcharge on the entire $1.5 million — $60,000 annually — not a marginal rate on the excess above $1 million.
Condo Units vs. Billing Lots
Condominium properties create the most confusion in BBL identification because individual units typically receive separate tax lots while the building maintains related billing or parent records.
A 20-unit condo building might have BBL 1-1234-1 for the underlying land and BBLs 1-1234-1001 through 1-1234-1020 for individual units. The surcharge notice will reference the specific unit lot, not the building's master record.
Co-op buildings operate differently. The building itself holds one BBL, and individual shareholders receive surcharge determinations based on their proportional shares of the building's total market value, calculated through statutory share ratios under Administrative Code sections 11-3201 and 11-3202.
Reading Your DOF Property Profile
The DOF Property Profile at webapps.nyc.gov/dof displays the official property record tied to your BBL, showing address, ownership, building details, and crucially for the surcharge, the market value figure.
Look for the 'Market Value' line under Property Valuation — this number, not the assessed value, determines your surcharge exposure. The assessed value for condos and co-ops runs roughly 45% of market value and applies only to regular property taxes.
The profile confirms whether your record matches the BBL on any surcharge notice you receive. For condos, verify that the unit number and BBL align between the notice and the profile to ensure you're reviewing the correct tax lot.
Market Value: The Surcharge Base
The DOF's adopted rules state explicitly that 'the surcharge is based on market value, not assessed value' and that surcharge calculations use 'DOF market values calculated for real property tax purposes.'
This distinction matters significantly. A condo with $2 million market value and $900,000 assessed value would face a 4% surcharge on the full $2 million — $80,000 annually — despite widespread confusion in early commentary suggesting the assessed value controlled.
The market value appears on your annual Notice of Property Value and in the DOF Property Profile. Co-op shareholders receive unit-specific market values derived from the building's total through their share ratios.
Current Deadlines and Exemptions
Property owners who received DOF's 'You may be subject to...' notices have until October 6, 2026, to apply for primary residence exemptions, following two extensions from the original August deadlines.
The exemption covers properties serving as the primary residence of the owner or immediate family members, including spouse, children, siblings, parents, grandparents, or grandchildren. A 12-month arm's-length lease to a natural person also qualifies.
Non-primary status gets determined as of January 5 preceding the fiscal year, not by how many days the owner spent in the unit during the year. Owners have 30 days from notice transmission to appeal DOF's determination.
Geographic Concentration
The surcharge hits Manhattan hardest, with ZIP codes 10019 (Midtown West) and 10012 (SoHo/NoLita) each showing more than 900 condo and co-op units above the $1 million threshold, according to Conquest's analysis of DOF's July 2026 Supplemental Market Value Roll.
Brooklyn houses represent the second-largest exposure group, with roughly 3,300 units above the $5 million threshold for single-family properties. These face surcharge rates starting at 0.8% of full market value.
The Bronx shows 77 houses above the threshold, while Queens and Staten Island each show fewer than 40 exposed units across all property types. The concentration reflects the city's luxury housing geography.
What to Watch Next
First surcharge payments come due January 1, 2027, for the fiscal year that began July 1, 2026. DOF will mail final determinations after processing exemption applications through the October 6 deadline.
Phase 2 of the surcharge begins July 1, 2028, when condo and co-op valuations shift toward comparable sales methodology and rates align with the house schedule of 0.8% to 1.3%. The transition could significantly alter individual surcharge amounts.
Use Conquest's free DOF market value checker to verify your property's current valuation and potential surcharge exposure before the exemption deadline.
Frequently asked questions
How do I find my BBL number for the pied-à-terre tax?
Your BBL (borough-block-lot) number appears on property tax bills, DOF notices, and can be found on the DOF Property Profile at webapps.nyc.gov/dof. For condos, individual units typically have separate BBLs (like 1-1234-1001), while co-op buildings have one BBL for the entire building with shareholders receiving determinations based on their proportional shares.
Is the pied-à-terre tax calculated on market value or assessed value?
The pied-à-terre surcharge is based on market value, not assessed value, according to DOF's adopted rules. For example, a condo with $2 million market value would face a 4% surcharge on the full $2 million ($80,000 annually), even if the assessed value is only $900,000.
When is the deadline to apply for the primary residence exemption?
Property owners who received DOF's 'You may be subject to...' notices have until October 6, 2026, to apply for primary residence exemptions. The exemption covers properties serving as the primary residence of the owner or immediate family members, including spouse, children, siblings, parents, grandparents, or grandchildren.