The man with the neatly trimmed beard and his blond companion decided on the 200-year-old English desk, and the Washington antique dealer was delighted. The price -- $15,000 -- was fine, the man said, but he had to pay in cash.

No problem, said the antique dealer. And he promised to keep the transaction secret, thereby violating a 1984 federal law that requires businesses to report to the Internal Revenue Service any cash transaction of $10,000 or more -- a law intended to restrict the laundering of drug payments and other "dirty money" through legitimate commerce.

Money talks, cash whispers.

The man and woman on the shopping trip were congressional investigators, who called on 79 businesses in nine cities -- including Washington -- to find out how easy it is to pay quietly for luxury items in cash.

Whether it was imported cars, diamond-studded Rolex watches or oriental rugs, the merchants were only too happy to take the cash and keep quiet about it, the investigators told the House Ways and Means Committee yesterday. Only three businesses refused to take the money without reporting it or accept a false name, further concealing the transactions. "You can even use Mickey Mouse," one car salesman told an investigator.

Barney Gomez, a special agent of the House Ways and Means oversight subcommittee, told that panel yesterday: "The merchants we dealt with were eager to take our money without much concern about our identity or the tax code reporting requirements."

Subcommittee members were aghast. Chairman J.J. Pickle (D-Tex.) called it "shocking that businessmen throughout the country are conniving with customers" to evade the law.

"I think this is the most shocking testimony I've heard in my 12 years in the U.S. Congress," said Rep. Beryl Anthony (D-Ark.).

Washington figured prominently in the investigation. The antique dealer here indicated to the investigators that in addition to not reporting the purchase of a $15,000 desk, he probably wouldn't be paying income tax on his profit, either.

" ... It just so happens that this is one of the pieces I don't have on inventory, just for cash deals like this," he told the probers.

When the investigators told a real estate salesperson on Capitol Hill they wanted to pay cash for a $259,000 condominium and keep it quiet, the salesperson suggested ways to circumvent the law by using cashier's checks and money orders, which do not have to be reported.

In addition, the salesperson referred the investigators to "an attorney who works with cash purchases and he is aware of your situation. I want you to work with him."

In fact, of 10 businesses visited in Washington, every one was willing to take cash without reporting it and every one was willing to take a false name. A third of the businesses even had helpful suggestions about how to evade the law, according to the investigators.

Nationally, the only businesses to reject an unreported sale were a jeweler in New York City and a car dealer and a jeweler in Minneapolis.

The panel did not release the names of the businesses involved, but staff members said they included some big, well-known national chains. Pickle said the full investigative report, including the names, will be turned over to the IRS. The investigators said they have names and addresses to go with their reports, including the name of the lawyer mentioned by the Capitol Hill real estate agent.

The investigators did not wear recording devices, nor did they actually buy the items they discussed. If they had, they said, they could have laundered $4.1 million through the 76 cooperating businesses in a little over a month this summer.

The level of cynicism by the businesses was impressive. A jeweler in Atlanta, where the investigators were looking at two Rolex watches priced at $17,408, said he knew he had to report any transaction over $10,000 and that the IRS had been looking at the store's books.

"The jeweler then lowered his voice and said, 'Let's talk a little quieter because we still have a couple of IRS people in the back looking at our records,' " the investigators said. The jeweler then suggested splitting the purchase into two transactions to avoid the reporting requirement.

The investigators probed to find out whether the merchants were aware of the requirement -- most were -- and about why it had been imposed. Merchants commonly replied that it was to help law enforcement officers catch drug dealers.

The investigators also attempted to arouse suspicion by saying they had to bring the money from down south or that someone named "Carlos" would bring the cash by in a few days, but none of the sellers batted an eye.

While negotiating over a $30,500 Audi 100, a car dealer in San Antonio told the investigators cash was "no problem; remember, we sell Porsches here."

Businesses that do engage in a $10,000-plus cash transaction are required to file Form 8300 with the IRS. However, Senior Deputy IRS Commissioner Michael J. Murphy acknowledged, "There is inadequate compliance."

So far in 1990, a grand total of four Form 8300s have been filed in the District this year. Only 15 were filed in the city last year and 11 the year before, said Thomas K. Arnold, the panel's assistant counsel.

Arnold noted that the law contains a significant loophole in that it defines cash as currency and coin, thus excluding cashier's checks, money orders and other cash-like instruments from reporting. Several members of the panel suggested that the provision be tightened, but Assistant Treasury Secretary Peter Nunez cautioned that such a provision might "end up capturing every business transaction that takes place."

Murphy noted that banks have long had a similar reporting requirement, but not until the successful prosecution of the Bank of Boston in 1985 was it much observed. Before the prosecution, banks were filing fewer than 70,000 reports a month, Murphy said. Today the figure is 500,000.