Occidental Petroleum Corp., one of the fastest growing oil companies with earnings of nearly three quarters of a billion dollars last year, capitalized yesterday on a controversial section of the 1981 tax bill designed to help ailing companies like Chrysler or International Harvester.

The Los Angeles-based firm with major oil holdings in the North Sea, Peru and Libya "sold" tax breaks on $94.8 million worth of equipment to Marsh and McLennan Co., a New York insurance and investment company.

The oil company qualified for the tax break despite its high earnings because it makes almost all its profits from foreign sources. Over the past three years, Occidental has paid no federal tax in the United States.

The deal is based on a section of the tax bill that allows corporations with little or no profits to sell off tax credits and depreciation to profitable firms that can then use the shelters to protect earnings from federal tax liability.

These deals--which amount to the buying and selling of corporate tax breaks--are consummated under paper transactions called leases.

The leasing provision was added to the Reagan administration tax bill to give marginal companies a share of sharp reductions in corporate tax liabilities so that the ailing companies could better compete.

Yesterday, in fact, the Treasury Department issued revised regulations governing leases that lawyers involved in private deals said were designed to allow Chrysler and other firms facing the possibility of bankruptcy to sell off their tax credits and depreciations.

What makes the Occidental transaction unusual is the fact that the oil firm, while reporting profits last year of $710.8 million, has almost no domestic earnings against which to write off tax credits and depreciation.

"We are a very profitable company," George Reese, an Occidental spokesman said. "The champion growth company of the Fortune 500."

Reese noted that despite the profits, which through the third quarter of this year have reached $456 million, Occidental is "not making enough domestic earnings to take advantage of our tax credits."

Instead, the firm will get a cash payment of somewhere between $20 million and $30 million from Marsh and McLennan in return for selling the tax breaks on the $94.8 million in investments Occidental has made in chemical plant and coal mining equipment.

In its 1980 annual report, Occidental said it paid no U.S. federal taxes in 1980, 1979 or 1978, although it paid foreign taxes of $1.95 billion in '80, $1.36 billion in '79 and $827 million in '78.

During those three years Occidental showed losses in the United States while reporting a profit of $5.7 billion overseas.

The firm was able to achieve this distribution of taxation while reporting that $7 billion of the $12.7 billion in total revenues in 1980 were from locations in the United States, and $3.9 billion of $6.2 billion in identifiable assets were in the United States last year.

Of the oil production, which is the major source of revenue, only 5,000 barrels a day were produced in the United States, while 573,000 barrels a day came from Libya, Peru, the United Kingdom, Bolivia and Canada.

For the insurance and investment firm of Marsh and McLennan, the tax breaks will mean, according to William Duggan, vice president for accounting and taxation, increased earnings per share of 3 cents to 5 cents this year and a total of about 50 cents over the 15-year life of the leases.

While both firms refused to discuss precise terms of the lease arrangement, the basic pattern of most such transactions under the new law goes as follows:

A company that has invested in equipment but has low or no profits against which to write off the tax breaks can "sell" the equipment to a profitable firm. The purchase price is based on a negotiated percentage of the value of the tax breaks to the profitable company.

The profitable company then "leases" the equipment back to the firm that originally bought it for a rent equivalent to the cost of paying off the purchase price. At the end of the lease, the transaction normally calls for the equipment to be sold back to the original purchaser at a nominal price.