Last January, 36-year-old Ron Berger of Portland, Ore., was asked by his accountant to make a choice: Maintain a daily mileage log or surrender the keys to his company car. Berger opted for the latter.

"It's not my style to keep those kind of records," explains Berger, president and chief executive officer of National Video Inc., a $90-million-a-year franchiser of video stores. "Also, I don't have time."

Neither, it seems, do numerous other small business owners.

Accountants from New York City to Los Angeles report that as many as half of their small business clients are giving uo their company automobiles rather than tackle the harsh paperwork demands of the Tax Reform Act of 1984. Those requirements include not only the maintenance of a detailed daily diary (listing, at a minimum, the mileage, date, place, and purpose of business travel), but also the painstaking separation of business use from personal use.

There is, however, at least one way companies can get around the strict record-keeping rules: Boost the salaries of executives, and ask them to pay for their cars out of their own pockets.

The advantages of the move are clear-cut: The company may deduct the full cost of the pay hike, and it avoids responsibility for maintaining mileage logs. The employee, meanwhile, may claim a personal tax deduction for automobile expenses (IRS Form 2106), so long as he or she keeps the daily diary.

But the strategy has its drawbacks. One accountant cautions that in the case of employee shareholders, the Internal Revenue Service may, at the time of an audit, interpret this increase as unreasonable compensation. But, he concedes, the possibility of that happening is remote.

The tactic can also be expensive for a company to implement, says Robert Haddad, a tax partner in the Boston office of Price Waterhouse. "The question," he says, "is whether you want to leave the person in the same net position on an aftertax basis."

Berger, for example, didn't plan to take a personal deduction for automobile expenses. So his corporation's board of directors voted to raise his pay in an amount equal to the loss of the company car, plus any income taxes that would be due on that sum. It ended up costing the company nearly twice as much on a before-tax basis as the annual cost of Berger's automobile lease.