A controversial provision in the 1981 tax bill allowing corporations in effect to sell tax breaks they cannot use was engineered in large part by three former Treasury Department officials who now represent companies standing to reap significant shares of the $27 billion bonanza over the next six years.

Their success in winning approval of what amounts to a backdoor federal tax subsidy to unprofitable companies reflects the power exercised by the business community in the development of the administration's $749 billion tax bill.

The new provision permits corporations to enter into lease transactions existing more on paper than in fact--a kind of fiscal netherworld in which businesses with low profits, or none, can "sell" unusable tax credits and depreciation deductions to profitable firms.

The Treasury Department estimates that this one section of the bill will result in lost revenues totaling $27 billion through 1986, although many business executives and lawyers in the field believe the figure will be far higher.

The key figures behind the administration's decision to adopt the provision, each of whom considers it to be an economically sound way of encouraging investment and of spreading the tax breaks evenly in the corporate community, are the following:

* Ernest S. Christian Jr., a partner in the lobbying firm of Patton, Boggs and Blow whose clients include the Chrysler Corp., which is already planning to "sell" its tax credits. Christian, legislative counsel for the Treasury in 1973-74 and deputy assistant treasury secretary for tax policy in 1974-75, said he has been working overtime since the passage of the legislation, putting together deals in which low-profit firms or those running in the red will "lease" investments exceeding $1 billion to profiable companies.

These leases, he said, really amount to the selling of $560 million or more in tax breaks over the next five years, of which $190 million translates into tax breaks for the current year.

* Charls E. Walker, of Charls E. Walker Associates, whose status amoung Washington lobbyists has reached its zenith with the election of President Reagan. Walker, under secretary of the treasury from 1969 to 1972 and deputy secretary of the treasury in 1972 and 1973, includes among his clients such capital-intensive companies as Ford Motor Co., Bethlehem Steel Corp., American Airlines and Trans World Airlines, all of which would be unable to profit fully from the basic elements of the business tax cuts without the ability to "sell" tax breaks.

Frederic W. Hickman, assistant treasury secretary for tax policy from 1972 through 1975. Hickman is widely credited by colleagues with coming up with the basic leasing concept adopted. A partner in the Chicago law firm of Hopkins, Sutter, Mulroy, Davis and Bacon, Hickman said he was putting together deals on a scale similar to that of Christian, about $1 billion.

These three men played critical roles in the leasing tax provision: Hickman producing the idea, Walker and the chief executive officers of his corporate clientele "softening up" Treasury officials reluctant to take a provision that might appear to be a federal subsidy, and Christian nurturing the provision through the complex paths from the Senate Finance Committee to the Senate floor into the House version and finally through the House-Senate conference committee.

The drive to create the new mechanism grew out of the fact that the basic business tax cut was larger and offered more benefits than many companies could use.

The basic cut took the form of a depreciation speedup, allowing companies to depreciate new investments at a rate significantly faster that the actual useful "life" of the machinery, buildings, cars, trucks purchased. But for companies with little or no taxable income, these accelerated deductions, along with the existing 10 percent investment tax credit, were of no use: They had no income against which to write off the investments.

Christian said experts knew from the outset that not all companies could take full advantage of this basic tax cut.

Walker, who has been representing a group of companies operating in the red or with only marginal profits -- airlines, mines, Ford Motor Co., steel companies -- had, as a member of the Reagan task force on taxes, unsuccessfully pressed for a concept of "refundability" to help such companies.

Under refundability, a low- (or no-) profit company that makes an investment would get a direct payment from the federal government in place of the unusable 10 percent tax credit. The idea would not sell in Republican circles, where it looked like a subsidy to companies unable to make it in the free market.

A political strategist of no small will or influence, Walker engineered a meeting in March between the chief executive officers of what had become known in the lobbying world as the "refundability group" and Treaury Secretary Donald T. Regan. The administration was still unwilling to go the route of refundability, but a task force was appointed, ultimately headed by William S. McKee, tax legislative counsel at Treasury.

A key argument Walker and his clients used was that the massive new tax breaks created by the legislation posed the danger of encouraging a breakout of corporate takeovers: profitable companies would find it worthwhile to buy unprofitable companies just to pick up the tax breaks.

During this period, Hickman, who shares a number of clients with Walker, began to press for the concept of "leasing" as an alternative to refundability.

Leasing, Hickman suggested, offered a way to create a corporate marketplace in tax shelters without the "emotional excess baggage" of appearing to be federal subsidies. "This was a way to sort of sweep the slate clean," Hickman said.

As an example: an automobile company, hypothetically called Chryford, spends $100 million for new equipment to retool its plants. Chryford has been operating in the red and consequently cannot use the investment tax credit, worth $10 million, or the accelerated depreciation, worth $46 milllion over five years to a profitable company.

Under the new law, Chryford could, within 90 days of buying the equipment, go to a profitable company -- a computer or oil company, for example -- and in effect "sell" the equipment to the profitable company.

The profitable company has absolutely no interest in owning the equipment, except for the resultant tax advantages. In fact, under the exceptionally loose law governing this transaction, the profitable company does not even have to take legal title to the equipment, just something called "tax title," according to congressional aides. Ownership, property tax liability, responsibility for upkeep, insurance coverage and everything else stays with Chryford.

Using a model developed by Peter K. Nevit, president of Bankamerilease, the "lease" between Chryford and the profitable company could be structured as follows:

The profitable company buys the equipment from Chryford and gives a down payment of $15 million for the equipment, effectively reducing Chryford's purchase cost by that amount. At the end of five years, the profitable company agrees to "sell" the equipment back to Chryford for one cent.

The profitable company would immediately claim the investment tax credit of $10 million and the first year of depreciation, or $6.9 million, for a total tax break of $16.9 million. Chryford would be ahead by $15 million and the profitable company is ahead by $1.9 million.

For the next five years -- the accelerated-depreciation period for the equipment -- the profitable company would "pay" Chryford annual payments of $25,356,820 (principle and interest at 15 percent on the $100 million) and Chryford would pay a "rental" or "lease" fee back to the profitable company of exactly the same amount. These payments would cancel each other.

Until the last of the five years, the profitable company would be able to deduct depreciation on the equipment, reducing its tax liability by a total of $10,143,200 over four years. The profitable company would owe this same amount to the federal government as a tax liability in the fifth year, but the money for those four years would function as the equivalent of an interest-free loan of $10,143,200.

In sum, Chryford gets to buy the equipment at a $15 million discount, and the profitable company gets $1.6 million out front and a four-year interest-free loan totaling $10,143,200.

Asked about his interest in the provision at this point, Christian said that until the concept was adopted by Treasury he had no clients with a direct interest in leasing as a way of shifting tax benefits.

But soon after the approach was accepted, "it was at that stage that I had from then on a very substantial interest in the matter and spent a lot of time working on the subject," he said.

Christian contends that the leasing provisions of the 1981 tax bill are "marvelous" and will emerge as "one of the most important developments in the tax law."

As for providing the legal work for lease arrangements, he said, "In one form or another, I'm probably involved in close to a billion dollars. . . . I've been working hard, that's all I can tell you."

Hickman said he had picked up about the same amount of business. "I think that our office and Christian's office, because of the fact that we were involved in the genesis of the thing, . . . undoubtedly we are heavier in it than the normal office."