Hundreds of District of Columbia homeowners have protested real estate tax bills they think are too high. City officials say most are too high because the taxpayers failed to file proper forms.

The issue arose after tax bills were mailed last week to city property owners, who owe the first installment by Sept. 17.

Kenneth Back, director of the D.C. Finance and Revenue Department, said about 600 homeowners complained Monday and hundreds more joined them yesterday to say they were not granted either the lower tax rate for single-family homes or the homeowner's exemption of taxes on the first $9,000 of the assessed value of their dwellings.

Back said the department granted both tax benefits to all qualified taxpayers who filed the necessary affidavits by a well-publicized July 2 deadline. But he admitted that some may have fallen between the cracks, "and if somebody says they filed [by the deadline], we are going to investigate."

Three taxpayers who contacted The Washington Post said they were told by the person who answered the telephone at the tax office that many of the affidavits were received but not processed.

Both Back and Alfred L. Richards, chief of the finance department's assessment services division, flatly denied this.

"We know we have processed everything we have gotten," Richards said. "One woman came to the counter today hollering and fussing. And, do you know? She had the affidavit in her purse, the form she should have filed two months ago."

Under the city's newly revised tax program, taxes are assessed this year at three levels -- owner-occupied dwellings, rental properties with up to five units and commercial properties, including large apartments.

Owner-occupied dwellings qualify for the lowest tax rate, $1.22 for each $100 of assessed valuation, plus an exemption on the first $9,000 of valuation. The owner of a dwelling assessed for $60,000 could save $139 in taxes below the tax rate for rental properties if the necessary form were filed and received on time by the finance department