Title: NYC Property Tax System Undervalues Co-ops and Condos, Experts Urge New Valuation for High-End Second Homes

When New York Governor Kathy Hochul and Mayor Zohran Mamdani unveiled their plan last week to tax second homes worth more than $5 million, the headline grabber was the projected $500 million annual revenue stream aimed at chipping away at the city’s budget deficit. But peel back the policy announcement, and what you identify simmering underneath is a far more consequential issue for anyone who owns or is considering buying property in dense urban cores like Manhattan’s Upper West Side or Brooklyn’s Park Slope: how New York’s deeply antiquated property tax system fundamentally misvalues co-ops and condos, setting the stage for inevitable legal challenges whenever the city tries to target high-value real estate.

This isn’t just theoretical friction. As detailed in recent reporting from CNBC and Habitat Magazine, the city’s current method for assessing co-ops and condos for tax purposes is legally mandated to treat them as if they were rental buildings, not as individually owned units. Under New York State Real Property Tax Law Section 581, the Department of Finance must use comparable rental properties to determine value—a process that systematically drags down assessments because those comparables often include rent-regulated units generating below-market income. The result? A Park Slope brownstone co-op that recently sold for $2.3 million might be assessed for tax purposes at a fraction of that, while a truly comparable market-rate rental down the street bears little resemblance to the actual economics of owner-occupied cooperative living.

What makes the proposed pied-à-terre tax particularly volatile is that it doesn’t just rely on these existing assessed values—it intends to tax based on actual market value for units over the $5 million threshold. This creates an immediate disconnect: the city’s own tax infrastructure is built on a foundation known to undervalue the very assets it now seeks to tax more aggressively. As Robert Pollack, senior partner at Marcus & Pollack and a noted expert on NYC real estate taxation, warned in Habitat Magazine, “The assessed values are absurdly low. They are not representative of market values.” When the city attempts to apply a new surtax layer onto this unstable base, the inevitable result, according to both tax attorneys and appraisers cited in multiple sources, is a wave of litigation challenging how the city determines what constitutes a “$5 million second home” in the first place.

The implications ripple far beyond the billboards of Billionaires’ Row. Consider the brownstone-lined blocks of Fort Greene or the pre-war cooperatives lining Riverside Drive—neither qualifies as a pied-à-terre in the traditional sense, yet both exist within a tax system where their assessed values bear little relationship to what they’d fetch on the open market. Should the city’s Department of Finance, as speculated in recent analyses, shift toward using only market-rate rentals as comparables (a change currently under legal scrutiny in cases like Tax Equity Now NY LLC v. City of New York), hundreds of thousands of co-op and condo owners could see their tax bills jump overnight—not because of a new tax, but because the long-suppressed market value of their property finally surfaces in the assessment roll.

This tension between outdated assessment mechanics and modern real estate economics isn’t new, but the pied-à-terre tax has brought it into sharp relief. For decades, the rental-comparison method served as a crude equalizer, keeping taxes artificially low for owner-occupied units in buildings with significant rent-regulated populations. But as those regulated units diminish and market-rate rents climb, the artificial suppression of assessed values creates growing inequity—not just between owners and renters, but between different neighborhoods and building types. The city’s own Comptroller noted in a 2024 fiscal analysis that this method “limits DOF’s flexibility in the matching stage and lowers valuations in the aggregate,” a diplomatic way of saying the system is increasingly out of step with reality.

Given my background in urban policy analysis and housing economics, if this trend impacts you as a co-op shareholder or condo unit owner in a community like Bedford-Stuyvesant or Astoria, here are the three types of local professionals you need to understand how these valuation shifts could affect your property taxes:

Property Tax Certiorari Attorneys

Look for lawyers who specialize in challenging NYC tax assessments, particularly those with experience in Article 7 proceedings before the New York State Supreme Court. Key credentials include a track record of successfully reducing assessed values for co-ops and condos in buildings with mixed-income rental comparables, and familiarity with recent case law like the Tax Equity Now litigation. They should understand how to build a case using actual sales data, income statements, and comparable unit sales—not just rental schedules—to demonstrate true market value.

Co-op/Condo Financial Advisors with Tax Expertise

Seek financial advisors who work exclusively with cooperative corporations and condominium associations, ideally those who have guided boards through reassessment periods or budget crises triggered by tax revaluations. They should be able to model how shifts in assessment methodology (e.g., from rent-regulated to market-rate comparables) would impact your building’s overall tax burden and monthly maintenance, and advise on reserve funding strategies or potential abatement applications. Crucially, they must understand the interplay between the city’s tax roll and your building’s underlying mortgage or underlying financial structure.

Licensed Real Estate Appraisers Specializing in Co-ops and Condos

Not all appraisers are equal in this niche. Prioritize those certified by the Appraisal Institute who regularly work with NYC co-op boards and condo associations on matters of valuation for financing, sales, or tax grievance. They should demonstrate deep knowledge of how Section 581 shapes assessment practices, and be able to critique the Department of Finance’s comparable selection process—particularly its use of rent-stabilized versus market-rate rentals. Their reports should adjust for factors like flip taxes, underlying mortgages, and sponsor interests that pure rental comparisons ignore.

Ready to find trusted professionals? Browse our complete directory of top-rated real estate tax specialists in the new york city area today.