"REGULATIONS THAT would make the Gestapo proud," snorted one congressman.

"Joe and Martha Six-pack shouldn't have to hold degrees in accounting just to be able to file their taxes properly," said another. "Let us repeal and repent," a third added. The subject of these laments? A change in the tax law attempting to crack down on taxpayers who claim illegal business deductions -- amounting to at least $3 billion a year -- for automobile use that is actually for personal reasons.

Who is affected by this? Tax law has never allowed businesses or individuals to deduct expenses for commuting -- only for other trips directly related to business purposes. And most workers who use their own cars for business reasons are reimbursed directly by their employers after submitting records of their mileage and the purpose of their trips. Others, such as full-time farmers and traveling salesmen, actually use their vehicles almost entirely for business.

Typically, the trouble has arisen in cases where a company (or personal corporation) has bought a car for an owner or high-level executive for general use. These people are supposed to declare the value of their personal use of the car (including commuting) as taxable income or to reimburse the company. But often they greatly underestimate personal use. Or a doctor, for example, might deduct most costs of a car even though relatively little of its use was for house calls.

Internal Revenue Service requirements for documenting business use formerly were relatively vague and laxly enforced. Last year, reacting to studies showing widespread abuse, Congress decided to start requiring "adequate contemporaneous records" -- the same sort of records that people manage to fill out to claim reimbursements from their employers.

Unfortunately, when the IRS first issued detailed rules under the new law, it didn't take into account legitimate complaints of farmers, traveling salesmen and other constant business travelers. But in February the rules for these groups were greatly simplified. Now they are actually less complicated than rules for claiming many other business deductions, such as business lunches and cab fares.

For example, people who use a car for most of the day to call on clients or customers, make deliveries or do other business can decide not to keep any records at all and simply claim 70 percent -- 80 for farmers -- of the car as business use. Or a salesman making an out-of-town trip or a person making a series of daily deliveries could make a single entry in a log for the period. If the vehicle is kept at a place of business -- or if a person such as a policeman is required to use a business vehicle for commuting -- no daily logs would be required.

Perhaps the taxpayrs and business lobbyists who have been flooding Congress with complaints are not aware of these simplifications. And perhaps there are other special exceptions that the IRS needs to consider. But before Congress junks the rule entirely, it ought to remind itself that a major reason that the deficit is so big -- and the tax system so unfair -- is that so many people have found ways to avoid paying their fair share of the tax burden.