Challenging the accuracy of the city’s entire tax roll, the union has charged that understaffing has more than tripled the revisions of condo assessments this year. In February, the Dept. of Finance announced that it would send out about 100,000 “Change by Notice” letters to the owners of Class 2 properties — co-ops, condominiums and apartment buildings.

Ordinarily, the department revises the assessments on about 30,000 properties each year. A Finance representative blamed the revisions on reductions in the rent that owners can get for their condos.

But David Moog, president of Assessors, Appraisers and Housing Development Specialists Local 1757, said downsizing caused the problem. He ridiculed the official explanation, noting that the assessed value of condos is based on criteria set by state law, not by market rents.

“The original assessment was not accurate because of inadequate staffing,” Mr. Moog told the Public Employee Press. Over the past two years, the department has reduced its assessing staff by 25 percent to 135 positions. Last May, in a white paper report, DC 37 said that the city could bring in an additional $57 million a year by rescinding the layoff of 29 property tax assessors and assistant assessors and adding 50 more.

When the preliminary assessment was released in January, Finance Commissioner Martha E. Stark said her agency had left behind its corruption scandal of recent years.

“With this assessment roll, we have begun an exciting era of renewed faith in the way we value people’s property,” she said. Ironically, only a month later, the department was forced to acknowledge that its revisions of Class 2 properties would be three times higher than usual.

Mr. Moog charged that the revision of the properties “questions the whole accuracy of the tax roll.” “Never has a more inaccurate tax roll been issued by the city,” he testified March 4 at a City Council budget hearing.

“By changing over 100,000 assessments, the department admits wide-scale errors in the 2004/05 tax roll,” Mr. Moog said. “Who knows how many missed assessments there are? How many new buildings and alterations were not properly assessed? How many parcels were undervalued — leaving the burden to be carried by the rest of the taxpayers?”

Mr. Moog concluded by calling upon the City Council to increase funding and return staff levels to what they were during the 2001-02 fiscal year.

— Diane S. Williams