Computer system may have had flawed algorithm.
Comptroller John Liu said the city's failure to warn homeowners about major changes in the way it assessed the value of co-ops and condominiums caused dramatic spikes in some property taxes last year.
The audit was released Thursday. It found that the Finance Department had relied too much on a flawed new computer system.
Queens homeowners were disproportionately affected.
The assessed values of some homeowners' units there last year jumped as much as 147 percent.
The Finance Department said it "works each year to assess more than one million properties transparently and accurately."