For the past six months Marilyn Tapscott has been tangled in a web of bad checks she didn't write.

She has received mysterious phone calls in the middle of the night, been threatened with lawsuits, and advised never to write another check.

The reason: Last March someone walked into Tapscott's downtown Washington office in the middle of the day and stole her checkbook, identification papers and credit cards.Since then someone pretending to be Tapscott has written at least $35,000 worth of checks to purchase, among other things, three microwave ovens, three crystal chandeliers, a set of bedroom furniture, several TV sets, $135 worth of shoes, $1,500 worth of meat, a home freezer, and a new leather coat.

"It's been a nightmare," said Tapscott, a 28-year-old secretary whose dilemma is made ironic by the fact that she works for one of the area's largest bank holding companies. That relationship did nothing, however, to prevent her from undergoing harassment of the type she thought was reserved for bad-check artists.

Some items: "A merchant came to my apartment building to tell the manager what a thief I was. A policeman came to my office saying he was going to arrest me. I had to cancel all of my own credit cards, and I'm afraid to write checks now because people may think I'm not the real Marilyn Tapscott.

"I'm supposed to be the victim, not the criminal," she said bitterly.

According to area police, Tapscott's problems are more severe than those faced by most people whose checkbooks are stolen. In most cases, the thief may write a dozen or so checks and then stop, fearing a trail of bad checks will lead detectives to his or her doorstep.

But in Marilyn Tapscott's case, neither the headaches -- nor the bad checks -- have stopped. There were, at last count, 98 checks, coming from merchants in every jurisdiction in the area. Not only has the thief, believed by police to be a woman in her late teens, exhausted all the checks stolen from Tapscott's purse. She also used Tapscott's identification papers -- and $40 of her own money -- to open a second checking account in Tapscott's name, thus extending her check-writing spree.

None of this should have cost Tapscott. By reporting the theft immediately and closing her checking account, she avoided any financial liability for the bad checks. That, however, has done nothing to stop police and merchants from dunning her for the bad checks.

A Federal Trade Commission official said yesterday that merchants know they have no right to make such demands on people like Tapscott, but because the recession has put a squeeze on their finances they are often seeking any way possible to recoup their losses.

Vienna police officer Roy Payne acknowleges he, too, went outside of normal channels by going to Tapscott's Washington office to discuss the checks. "Normally we don't go to someone's home or office, but I wanted to satisfy my own mind that she was not the suspect," he said in an interview.

Merchants say they, too, are caught in a bind. "God, it's a gamble, you are out to sell," says the Northern Virginia saleswoman who accepted bogus checks for the chandeliers. "Your first and foremost job is to sell, and so you trust people."

"The professional crook can steal us blind," says Joe Wilner, general manager of the Microwave Cooking Etc. chain, which was stuck with three "Marilyn Tapscott" checks totaling $1,200 in a two-day period.

"There's only so much we can do to protect against this," says Wilner. "If we really got tough we'd lose all our regular customers."

A security official at the Hecht's department store chain, where someone pretending to be Tapscott bounced a $346 check, agrees. "If we put in controls stringent enough to catch crooks we'd offend the honest public," he says. "This is just one of the costs of doing business in the Washington area."

Although precise figures on the number of checkbook burglaries aren't available (the crime is lumped together with all burglaries), area police say that the thefts are clearly on the increase. "It's the growth industry of crime," says Arlington Detective Lowell Glass, a member of the county's six-member check squad. "Three years ago two officers here could handle everything. Now we have six officers doing checks, and we could use more people."

Federal officials four years ago put the costs of stolen checks and money obtained with bogus identification at more than $10 billion annually, a level they say has undoubtedly increased.

Such figures are small comfort to Tapscott, a $13,000-a-year employe of Financial General Bankshares, whose 17th Street offices are one block from the White House. She was eating lunch down the hall from her office there when her purse was stolen.

"I closed my bank account right away and notified all the credit card companies, so I haven't lost any money," Tapscott says. "But I've lost a lot of sleep, and had a lot of people question my honesty."

Because she notified credit card companies immediately, she protected herself from any major loss, although so far she said only one charge -- a gasoline fill-up -- has been made. Federal law limits individual liability to $50 per stolen credit card, officials say.

Meanwhile, Tapscott has curtailed her own business dealings, fearing she will be embarrassed, or even arrested, by merchants who have been stung by her impostor. She writes checks only to the baby sitter, to pay for credit card bills, or to merchants she knows.

"It's been a nightmare for me," Tapscott says in a shaky voice. "I wish it would end."