They generally work in converted warehouses the size of football fields. They make an average of $14,000 a year. They prefer to say they're employed by the Treasury Department; these days, they're reluctant to mention the Internal Revenue Service.

"We get booed even in the best of times," said Donna Briggs, who works at the IRS' Kansas City service center, one of 10 tax-return processing facilities across the country.

"Unfortunately, people think we're fat hogs who make a lot of money and do little work -- especially this year," said Ron Knod, an employe of the Fresno, Calif., service center and president of the local chapter of the National Treasury Employees Union.

For taxpayer and tax worker alike, this has been a memorably bad year -- perhaps the worst filing season in the IRS' 123-year history.

The problems, blamed on the agency's new $103 million computer system, have delayed the processing of hundreds of thousands of returns, glutted taxpayer-information lines so exasperated callers got only a busy signal, and, in two known cases, led harassed IRS workers deliberately to destroy letters from taxpayers.

At the Fresno service center, IRS officials admitted in mid-May that workers had shredded about 60,000 letters. The employes' union charged that the motive was to win merit pay for managers by showing that workers were adhering to strict production timetables, when in truth they were running far behind schedule.

"I'm not going to go into motives," IRS spokesman Rod Young said. "I suspect it was done because of the press of doing an awful lot of work in a short period of time."

Young said the correspondence included responses and, in some cases, copies of canceled checks from taxpayers concerning IRS bills. He said the letters were destroyed only after the taxpayers' accounts had been checked and, if necessary, corrected; however, the taxpayers were never told the outcome of their cases.

At the Austin, Tex., service center, a supervisor apparently instructed an employe to destroy about 20,000 similar letters, Young said. When confronted with the charges, the supervisor resigned.

"We have no evidence in either of these cases that tax returns were destroyed," Young said. Nonetheless, individuals have expressed fears that their returns were lost or destroyed.

The General Accounting Office, a congressional watchdog, is investigating all 10 service centers. Young said IRS inspectors are also investigating the Fresno and Austin operations.

IRS officials insist that the worst is over. They say their employes have caught up with the backlog of work. In January, they were 69 percent behind schedule in processing returns; earlier this month, a spokesman said, they were lagging only 0.5 percent behind.

Nevertheless, the officials say the agency is likely to pay a record amount of interest for not mailing refund checks by the May 30 deadline. Last year, interest payments on late checks totaled $209 million.

IRS spokesmen won't estimate the number of households nationwide that will earn interest on their returns. But roughly 340,000 households served by the Philadelphia service center alone -- including 40,000 in Maryland and 10,000 in the District -- do qualify, center spokesman Jim Davie said. The Memphis service center estimated that 32,000 Virginia households have not yet received their refunds.

The average refund in the Washington area is $800, the IRS said.

The IRS has advised taxpayers to call the local offices to check on the status of their refunds. The Baltimore district office had been getting 13,000 calls a day, spokesman Don La Ponzina said.

Meanwhile, the 21,505 employes at the service centers have been working 10- and 12-hour days. For the first three months of the year, they logged 410,812 hours of overtime, compared to 158,708 overtime hours for the like period last year. More recent figures were not available.

The workers, predominantly female, describe a closely supervised, pressure-packed situation with heavy emphasis on production.

In the past five years, said Robert Tobias, national president of the National Treasury Employees Union, the number of returns to be processed has increased by 41 million (to a total of 101 million this year), while budget cuts have shrunk the work force by 5,200 people. The new computers exacerbated the problems, he said. But IRS officials say the replacement of the 20-year-old system was essential.

"We had to get used to a new computer while processing returns," said Davie of the Philadelphia service center. "But like I say, 'In order to test a snow tire, it has to snow.' "

Such explanations did not amuse people like Joanne Pisarchick of Elysburg, Pa., counting since February on an $800 refund.

"My husband's on strike. My shirt company closed. The IRS lost our refund. What else?" said Pisarchick. "Maybe we'll get a little interest, but believe me, that's no consolation."

People who have to refile will also receive interest, but they can expect to wait at least five additional weeks before receiving their checks.