Columbia Catering, a Rockville firm that caters most of the State Department's high-level entertainment, has been shut down by the Internal Revenue Service.

William Seltzer, head of Columbia Catering, said yesterday that the firm owes the IRS $85,000 and has been chronically late in paying its taxes because of the slow rate of payment by its customers. The Rockville premises, at 1776 Jefferson St., were padlocked at 4 p.m. Thursday, Seltzer said.

No IRS official could be reached for comment yesterday.

Seltzer said perishables locked inside his building included 2,000 cookies and $500 worth of strawberries, as well as freezers full of meat and other party foods. The closing left 200 of Washington's most experienced, black-tied waiters and 40 other employes, including gourmet cooks, filing for unemployment benefits, Seltzer said.

Seltzer said he arranged to have Ridgewell's in Bethesda, the area's largest catering firm, take over the $250,000 worth of parties he had scheduled this week and last, including Secretary of State George Shultz's luncheon yesterday for Pacific Basin diplomats. Seltzer said he supervised the luncheon with some of his staff, although they were not being paid for it, and that he would supervise the other functions his firm had planned to cater.

"We've had a time keeping up [on payments to the IRS] for over a year," Seltzer said. "We pay up and then fall behind again. We don't have enough capital. Right now, as I told . . . the IRS officer who closed us down, we are owed $100,000. Our customers are good for this; the money just hasn't come in yet."

Seltzer said he had been given a 10-day warning, which would have been up on Tuesday, "but [an IRS agent] came without warning at 4 p.m. Thursday."

Columbia is considered the third largest caterer in town, after Ridgewell's and B&B Caterers. Columbia is known for the lavish food it serves at cocktail parties -- where cloth napkins, not paper ones, are used -- and for its ability to seat dinner parties of up to 500 persons.