(MONEY Magazine) – First you panic. Then you feel guilty. No matter how honest you are, your heart sinks when you get a letter from the Internal Revenue Service, as I did six months ago, announcing that you've been targeted for a TCMP audit -- one of those killer audits from C.P.A. hell. The full title of this refined form of torture is the Taxpayer Compliance Measurement Program audit. Every three years, IRS computers pluck out roughly 55,000 tax returns at random for the TCMP -- one in 2,000 of all 110 million returns. Unlike a regular audit (of which there were 984,643 last year), where you must only provide proof of items that the IRS finds suspect, the lollapalooza TCMP demands that you verify e-v-e-r-y s-i-n-g-l-e line of your return, from your name to your bank account. That requires bales of supporting documents. The IRS uses its findings from the TCMP to determine its top-secret DIF formula -- the Discriminant Function scoring system that is used to flag questionable tax returns for regular audits. (By the way, you are probably off the hook -- at least for now. Your chances of being tapped for the TCMP this year have dwindled considerably, because all but roughly 10% of the notices were sent out between October and May.) My TCMP purgatory began last January outside my Deerfield Beach, Fla. condominium just north of Fort Lauderdale when my mailman handed me a letter with the all-too-familiar IRS envelope. My stomach knotted as I ripped it * open. I knew I was a likely target for a regular audit, since I'm a single, self-employed journalist who in 1988 deducted the cost of my home office, the business use of my car and high medical bills. But I felt physically ill when I began reading the computer-generated letter and realized I was headed for the notorious TCMP. Why had I been so dumb as to have written off that black velvet strapless dress as a business expense? Would they also challenge my home office? My donations to the Salvation Army? Having paid $197 to get my 1988 tax return prepared didn't ease my panic. The letter directed me to bring ''everything you need to support your 1988 tax return to IRS office at 300 Lock Road at 8 a.m. Feb. 16.'' I had about four weeks to comb through and decipher my 10 pounds of receipts, canceled checks, credit-card slips and other tax records. During that time, my friends told me horror stories they had heard about the dreaded TCMP. One said I'd have to verify my Social Security number by producing the card -- which, as my luck would have it, was locked up for the season at my mom's summer house some 1,700 miles away in Maine. Another insisted that the audit would take several days, maybe even weeks, and that I would have to return to the IRS office again and again. I tried to stay calm, but each time the subject arose I broke into a cold sweat. My C.P.A., Ned Fagg of the national accounting firm McGladrey & Pullen, did his best to calm me down. The day before the audit, as he and I sorted through my tax paraphernalia, he assured me that I was as prepared as I could be. When we arrived at 300 Lock Road in Deerfield Beach, about five minutes from my home, I found the IRS office disarmingly elegant: polished marble floors in the lobby and maroon carpeting in the large second-floor examining room, which was divided into intimate pods by gray tweed partitions. Examiner Valerie Allen, pretty, soft-spoken and uncommonly courteous, seemed about my age (32) and therefore a lot less threatening than I expected. I was imagining I'd face a crotchety old geezer with nicotine-stained fingers and a beer belly. After Allen ushered us into her cubicle, Ned and I pulled our ammunition out of my cardboard file box and the examination began. At first Allen's questions were innocent enough. Reading from a checklist, she asked: Have you been audited before? Do you have a copy of your 1988 return? Did you amend your return? Do you have a copy of your 1987 return? No. Yes. No. Yes. ''Now I'm going to ask you some questions about income items, some of them taxable, some of them not,'' she said. ''Did you sell anything? Have other jobs? Do you have a hobby that you sold anything from? Do you have any rental income? Any alimony? Did you win any prizes like the lottery? Any proceeds from gambling? Any gifts? Any grants? Any cash loans?'' So far, so good. Nothing hard here. Then, just as I was about to relax, she downshifted into a dagger-sharp, line-by-line grilling. ''Let's start with interest income,'' she said pointedly. Ned pulled out the 1099 forms that my bank and stockbroker had sent me. ''Now medical. Do you want to show me your receipts?'' This was a biggie. A health problem had put me in the hospital twice in 1988, once in Boston, and had entailed several return trips to the city. After Ned handed her the ledger I kept, Allen asked to see the canceled checks for my health insurance premiums. I pulled out five checks totaling $8,146.12. Then she asked, didn't my insurance company reimburse me for doctor bills? I explained that I had assigned benefits to the doctors. The checks I wrote were either part of my deductible or were for expenses not covered by insurance. About the pharmacies I had paid by check, she said: name one. I named two, but when I volunteered to fish out the receipts, Ned nudged me under the table. I got the message and shut up. He told me later that volunteering information -- any information -- is just an invitation to trouble. The next question came out of the blue. ''Why do you go to Massachusetts?'' she asked, looking me square in the eye. I explained that my doctors were highly regarded specialists at Massachusetts General Hospital. ''What are their names?'' Someone trying to pass off summer trips to Martha's Vineyard as a medical expense might have had a problem. I didn't blink. ''Dr. Charles Poletti and Dr. Lawrence Borges.'' She relaxed. Ned relaxed. I relaxed, knowing that she believed me. Charitable contributions? Allen looked at my receipts from the Salvation Army for seven boxes of clothes, an antique chair, assorted household items and a bike, all worth about $495. Nothing unusual. On to Schedule C and my freelance-writing income. ''Give me a brief description of your day-to-day operation,'' she said. I explained that most of my time was spent on assignments from the local newspaper, the Sun-Sentinel, and the rest on work for Money and Newsweek. She began peppering me with questions. Did I employ anyone? No. How long had I been a writer? Eleven years. Where was my checking account? Florida National Bank. And then, unexpectedly, came these: Did I keep cash mostly on hand or in the bank? In the bank. Did I have a safe-deposit box? Where? What were the contents? Don't ask me why. Maybe it was the strain. Maybe it was having my personal affairs subjected to a stranger's scrutiny. But as I answered her question about my safe-deposit box -- it contains my will, a living will, my condo documents and a personal letter to my loved ones to be read with my will -- something nearly gave way. I didn't break, but Allen was ready. Without looking, she reached for a box of tissues from the counter behind her and pushed it within my reach on the desk. It was nearly empty. Bank statements? She shuffled through my pile and kept them all to copy later. Another surprise question: Did I have my January 1989 bank statements? Actually, I did. Allen kept them for copying too. Next came trouble. Most people probably have something on their tax returns they feel a little queasy about. For me, it was my home office, basically a work area along a wall in my bedroom. I had been claiming deductions for my office since 1986. Now the chickens were coming to the home office to roost. Allen tiptoed into this subject by asking a one-word question. ''Insurance?'' Ned knew she was referring to my condo insurance write-off for the office. ''She has a total of $195, and she's got 13% of it,'' said Ned, describing the percentage of the insurance that I deducted because my home office takes up 13% of my apartment's square footage. I should have seen the next line of questioning coming. But I didn't, and I was broadsided. ''How many bedrooms do you have in your apartment?'' ''Just one.'' ''What section of your apartment do you use for your office?'' Fighting panic, I went with the truth. ''I have my office along the wall to the living room.'' ''So your office is in the living room?'' ''No, my office is part of the bedroom.'' There was a weighty pause. ''I have my computer, my computer desk, my printer, my filing cabinet, my books and my monitor,'' I said, the weight of my office settling on my heart. ''Um-hmmm,'' she said. ''Mortgage?'' I started to breathe again. ''She deducted $225 interest,'' Ned answered. ''Office expenses?'' % Here's where things got strange. Allen looked down the column in my ledger devoted to home-office expenses and thumbed through the receipts I had stuffed into an envelope. She let pass $21.15 for binoculars I had bought rather than accepting them gratis from a company I was writing about. But she zeroed in on $50 for attending an architecture conference. ''The publication I intended to sell the story to required me to attend,'' I said, and she accepted that. Allen then asked about two checks to a grocery and liquor store -- expenses for a dinner party I gave for a group of journalists. She noted that I hadn't written the business purpose on my checks. I opened my 1988 appointment diary and showed her where I had recorded my plans for the party, with the names of some of the people invited. After pausing for a few seconds, she moved on. The lesson was clear; from now on, I'd clearly separate my business and personal expenses in my ledger and note them on my checks. She proceeded to look at my log of miles driven for business and asked Ned why my mileage wasn't listed under car and truck expense. He explained that I had included it with my travel expenses. Then Allen spotted another squishy write-off: two checks to ABC Fashion for $90 each. I fessed up. ''If there is anything questionable on my return, this is it,'' I said. ''I didn't have a formal dress, and one of the companies I worked for had a black-tie Christmas party. I had a $180 dress made for the party, and I have not worn it since.'' She frowned. ''This category is supposed to be for costs associated with people you entertain to get business. If I were being real sticky, I would ask for a guest list of people at the party, then ask you to show me the business that resulted,'' she said. But she let the dress pass, and my heart warmed to the woman. After a few more routine questions, she left to copy the bank statements. Upon returning, Allen said: ''I'll go through these bank deposits and give you a call if they reveal any income that I can't account for. You'll get a letter in four to six weeks regarding the outcome. Go home and start on 1989.'' Two hours and 15 minutes after my TCMP audit began, it was over. In the weeks that followed, I tried not to think about the pending letter. But after seven weeks and still no letter, I called Allen. She told me that she had made a few ''adjustments'' to my return but had found no additional tax due. It turns out that wasn't unusual. In 1987, half the taxpayers who underwent TCMP audits owed no extra taxes, and of the 43% who did, the amounts were often less than $100. My TCMP audit isn't truly finished, though. Allen's findings are subject to review by her district office in Fort Lauderdale, so I probably won't know for sure how I came through until July. Yet even if I don't owe the IRS a nickel, my job as an IRS guinea pig didn't come cheap. For starters, Ned charged $675. And since freelance writers don't get paid for the time they don't work, the seven hours I spent organizing my records, meeting with Ned and in the audit itself are lost forever. I figure I could have earned at least an extra $100 if not for the IRS' snoopiness. I'll remember that if I ever wear my black party dress again.