When President Carter holds the final round of strategy sessions on his tax revision package later this week, one of the major sticking points will be what to do about business taxes. The question of how much tax relief to grant corporations - and how to go about it - is emerging as one of the most hotly debated issues in the entire tax reform effort. Some even question whether business needs a tax cut at all.

The issue is an emotional one. Business spokesmen such as former Treasury Secretary William E. Simon argue heatedly that tax relief is necessary to offset new energy costs and other recent tax changes that are crimping business investment. To deny corporations a tax break now "would mean continued stagnation in capital spending," Simon contends. And economists say investment levels must be stepped up if the recovery is to meet government goals.

On the other side, Rep. Charles A. Vanik (D-Ohio) argues that because of special deductions and preferences, too many big companies already pay far less than the 48 per cent of their U.S. income that the corporate tax rate implies. And Robert M. Brandon, director of Ralph Nader's Public Citizen Tax Reform Research Group, asserts flatly, "There is no justification for corporate tax relief right now."

Although the economic arguments can go on almost endlessly, there's one rationale that's pushing policymakers toward a sizable corporate tax cut: Needed or not, businessmen expect one. To refuse it could risk jarring already tenuous business confidence - and possibly endanger passage of the rest of the Carter tax revision program as well.

As such, the "business package," as it's known, is rapidly becoming the keystone of the Carter proposal - with everything else dependent, in a sense, on what the President decides about corporate taxes. "What Carter does here will bring out the lobbyists," says one longtime tax observer. "The business tax cut is needed as a sweetener for the rest of the package. The only questions are how big and what kind it should be."

How burdensome are corporate taxes? Proponents of a big business tax cut contend they've gotten so heavy they're seriously crimping both profits and investment. Conservatives complain that U.S. corporations are taxed far more heavily than their foreign competitors, that the U.S. tax structure unfairly penalizes savings and investment, that businesses are being strapped by inflation and government pollution-control requirements, and that companies are being threatened anew by President Carter's latest energy tax proposals.

Executives of ten of the nation's largest corporations personally told President Carter last week that business confidence was so low an even larger corporate tax cut would be needed than the $5 billion to $7 billion the administration is planning. Irving S. Shapiro, chairman of E.I. Du pont De Nemours & Co., warned that business was "deeply distrustful of government economic policy."

Murray L. Weidenbaum, director of the St. Louis-based Center for the Study of American Business, complains that the tax system places U.S. companies at a distinct disadvantage compared to foreign competitors. In the first place, Weidenbaum points out, the U.S. draws a far larger share of its total revenues from the corporate tax. "If you look at the corporate tax code provision by provision, U.S. business is taxed as heavily or more heavily than any other country," he says.

More important, America's tax code hits harder at income than at consumption - effectively discouraging savings and investment, he continues. In Europe, much of the total tax burden is borne by various forms of sales taxes, such as the value-added tax, which is passed on to consumers, he points out. But here, business' big tax is on corporate income, he asserts, and "every dollar saved automatically becomes a dollar taxed."

Alan Greenspan, economic adviser to former President Ford, argues that disparity has been exacerbated in recent years by congressional tax actions. "Ever since the Kennedy administration, the tendency has been to concentrate tax cuts on low-income persons and to close so-called loopholes which favored investors, Greenspan says. "As a result, the tax burden has shifted to increase the burden on capital and investment."

Simon and others argue that these forces taken together have seriously eroded corporate profits and rates of return. Now, Simon complains, President Cart*er wants to close off more incentives to investment and impose new energy taxes. "All this has really angered business," he says. "They're really getting strangled with this."

To be sure, Weidenbaum has a point about the tax burden on U.S. corporations. Statistics show that in 1972, for example, corporations provided 11 per cent of all government receipts here compared with a modest 5 per cent in West Germany, 6 per cent in France and 7 per cent in the United Kingdom and Italy. Only Japan was higher, with businesses there accounting for 24 per cent of total government revenues. But Japan's economy is different, too.

Moreover, new figures compiled by the International Monetary Fund show that the U.S. concentrates much more of its tax burden on income instead of consumption than do most other industrial countries. The federal government here gets 55.7 per cent of its taxes from levies on net income and profits, and only 5.6 per cent from consumption taxes. By comparison, in West Germany that proportion is split almost evenly, 20.5 per cent to 23.9 per cent.

The problem, however, as Weikenbaum himself concedes, is that the comparison is not entirely valid because the structure of, the American economy - as well as the U.S. tax system - is different from many of those abroad. In the U.S., for example, corporations account for some 70 per cent of all trade and business. In Spain, the proportion is 5 per cent. Other countries come out in between.

Moreover, U.S. tax law grants companies a spate of sizable deductions and preferences that bring the actual tax rate most corporations pay far below the 48 per cent usually cited. There are deductions for business expenses, rapid depreciation writeoffs, credits for taxes paid abroad, tax subsidies for exports, credits for investment in new equipment, and depletion allowances for oil or mineral exploration.

Although most tax experts scoff at Vanik's complaints about big corporations that pay no taxes on their U.S. income (the companies the congressman cites almost always are using the foreign tax credit, legally, to avoid double taxation on overseas income already taxed by other countries), figures show the average effective tax rate paid by U.S. corporations - that is, the actual tax they pay as a percentage of profits - now is 29.9 per cent, down from 40.6 per cent in 1960.

The rub is, as in the case of taxes on individuals' income, the tax laws treat corporations unequally. As a result, industries with large overseas operations or oil-drilling or real-estate holdings usually escape with relatively modest tax liability, while others - including many "basic" industries such as steel and auto manufacturing - are hit hard.

Even within the same industry, companies often pay widely different proportions of their income in taxes because of the deductions or preferences they are allowed. New figures by Tax Analysts and Advocates, a research group, show that the effective tax rates of major chemical companies last year ranged from 38 per cent for the Ethyl Corp. to 10.1 per cent for Rohm & Haas.

Because of this disparity, there's really no way to say accurately whether corporations are taxed too heavily or too little, Greenspan says.

To many tax analysts, the only real economic question is whether a tax cut would stimulate needed business investment - certainly the biggest short-term need for the recovery, and a serious longer-range consideration as well. Greenspan argues here that a corporate tax cut now" could improve" business performance, but adds that other uncertainties - such as the long-term inflation outlook and the worry over energy taxes - must be resolved before the gains can be expected to last.

Perhaps even more important, conservatives worry about the possible impact of ending the tax preference for capital gains - a key element of the President's tax revision proposals. Greenspan, for one, contends that closing off investment incentives could seriously dampen the long-range economic outlook.

If the corporate tax structure is okay, then why cut business taxes?

"Simply on grounds of equity," says Herbert Stein, the former Nixon administration economic adviser.

"It's not an economic issue," chimes in another analyst. "Business is just saying: "I want it."

The question is, how big a tax cut should business finally get, and what form should it take - a straight cut in the 48 per cent corporate tax rate, a boost in the investment tax credit, or a combination of several proposals?

At last report, Carter administration tax writers had decided on a combination package - a $5 billion to $7 billion net tax cut that would include a cut of 2 percentage points in the corporate tax rate, a significant broadening of the investment tax credit, and a reduction of the "double taxation" that results from taxing both profits and corporate dividends.

The tax cuts would involve some tradeoffs. At least part of the overall corporate tax reduction would be used to "make up for" closing existing tax preferences the administration regards as unjustifiable - such as ending the subsidy for Domestic International Sales Corporations, eliminating deferral of foreign-source income and phasing out the depletion allowance for mineral industries. Overall, however, the business tax cut still would amount to a net reduction of between $5 billion and $7 billion.

The rationale for spreading the corporate tax cut among several different tax-reduction provisions is that because of disparities in the makeup of U.S. corporations, none of the individual tax-cut proposals alone would benefit all kinds of industries. The plan is to provide modest cuts in a number of sectors so all companies can reap some tax relief.

But many businessmen already are complaining about the makeup of the package. Both conservative and liberal economists fret that by dividing the $5 billion to $7 billion into several modest doses, the administration actually may wind up dissipation the impact of the overall tax reduction. "My own choice would have been for a straight 5 per cent cut in the corporate rate," says Weidenbaum.

Then, too, there are complaints about the individual components! Economists are divided over the value of the investment tax credit. Studies show it is difficult to prove that the tax break actually spurs added buying of new equipment. Moreover, only about 35 per cent of U.S. corporations are in a position to take advantage of it.

Critics are even more vehement about the administration's reported plan for reducing double taxation. As described by some officials, the proposal would provide stockholders with a tax credit for 20 per cent of the estimated tax a company paid on its income. The shareholder would be sent a statement showing the credit to which he or she is entitled, just as wage-earners now are sent W-2 forms. The shareholder then would claim the credit on his or her individual income tax return - with lower- income taxpayers benefitting proportionately more than richer ones.

Tax experts generally oppose the move, first on broad philosophical grounds. "It would be adding enormous complexity to the tax system, and wasting an awful lot of money without providing much economic stimulus," complains Stanley S. Surrey, former Treasury tax expert in the Johnson administration. Other analysts fret that the shift could prt more pressure on companies to distribute their earnings as dividends, rather than plow them back into investment.

And Brandon grumbles that because "stockholders" so often are wealthy persons or other corporations themselves, the credit for dividend recipients too often would be simply "a tax cut for high-income people."

Analysts say it still is uncertain how business will react to the Carter tax package. Some contend the Wall Street reaction may depend more on how the White House proposes to deal with the critical capital gains issue than with the specifics of the business tax package. Although the capital gains tax is a tax on individuals, not a business tax, it's important to corporations because it affects investment patterns of stockholders. Administration officials say elimination of the present preference would make the tax code more equitable, and much simpler as well.

Liberals assert investors soon would adjust to any change in the treatment of capital gains because the maximum tax rate on unearned income would be lowered as well. But conservative analysts foresee a broader impact. A key question could be how the administration would treat capital losses. Unless investors are allowed to continue to use some of their losses to offset other income, the shift could prove a serious drag on investment.

Still, a sizable tax cut for business seems assured, if only because tax cuts for individuals always are accompanied by corporate tax reductions as well.