"What we're talking about, as to more revenue from business, is from those elements of business that have not been paying taxes . . . or paying very low taxes."

Was President Reagan right when he spoke those words at his news conference Thursday evening? Would his Treasury Department's tax simplification plan collect higher taxes only from corporations that haven't been paying?

The answer seems to depend on what Reagan meant by "very low taxes."

The Treasury plan's authors acknowledge that it would result in higher revenues from the corporate sector as a whole. They predict that the Treasury package, proposed in November, would increase revenue from corporate income taxes 25 percent in 1986 above that projected to be raised under current law, and by 37 percent by 1990. The increase over current law would be smaller in later years.

Revenues from individuals would decline an average of 6.5 percent over the 1986-1990 period.

It is uncertain what Reagan meant when he told reporters the plan would not "get a higher percentage from business." The share of federal revenues coming from the corporate sector would rise from 8.5 percent in 1984 to 15 percent in 1990. It would go up some under current law, but not by that much.

The revenue rise would come from abolishing numerous tax deductions and tax credits, more than offsetting the reduction in the corporate income tax rate from 46 percent to 33 percent.

Business representatives say that it is unlikely the additional revenues -- a total of $165 billion over five years -- could be raised only by levying taxes on profitable corporations that now pay no taxes. (Unprofitable firms have no tax liabilities.)

"You can't find enough companies that don't pay taxes to add up to $165 billion," said Jerry Jasinowski, chief economist for the National Association of Manufacturers. "We don't know the exact number, but we're talking about a big gap here."

Reagan has said he would "have to be convinced" of the need for a rise in corporate taxes. White House spokesman Larry Speakes said Friday that Reagan could change his "gut reaction" against corporate tax increases as proposed in the Treasury package "once he takes a look at the full implications of it."

A White House legislative strategy group that met Friday appeared to put off again the date when Reagan will do that. Members concluded that Reagan probably will not send tax recommendations to Congress until May.

Earlier, officials had hoped to decide by March on what Reagan would recommend to Congress. A Treasury official said the administration's recommendations might be made in consultation with congressional leaders and private groups rather than by sending a proposal to Congress.

Although specific breakdowns are not available, the Treasury plan's stated effort to equalize tax rates on different industries indicates that most of the new business revenues would come from low-tax sectors, not high-tax firms.

"I think he's Reagan about right," said Robert S. McIntyre, tax-policy director for Citizens for Tax Justice, a labor-funded tax-reform group. Based on his own studies, McIntyre estimated that, under the Treasury plan, 61 percent of companies would have a tax increase, 16 percent would have the same tax burden and 23 percent would get a tax cut.

Neither the Treasury Department nor the Internal Revenue Service has figures on how many profitable companies pay no taxes. The IRS says that 1,215,122 of the 2,812,420 corporate returns it received in 1981, the most recent year for which figures are available, did not pay federal income taxes. But those numbers don't distinguish between profitable and unprofitable firms.

The principal way tax rates would be equalized under their plan, Treasury officials say, is by replacing accelerated depreciation writeoffs with a less generous scheme.

The change, when fully implemented, plus lower statutory income tax rates for business, would raise the effective tax rate on the motor vehicle industry, now about 8 percent, to 31 percent, if no additional dividends were paid, according to Treasury figures.

For transport services, the rate would rise from 9 percent to 34 percent under the same assumptions. For mining (a category that ordinarily includes oil exploration and production), the rate would rise from 13 percent to 39 percent.

The high-tax industries would have smaller tax-rate rises: from 28 percent to 33 percent in fabricated metals, from 25 percent to 33 percent for food.

Half of the $22 billion increase in revenues from business predicted for the plan's first year would come from higher taxes on two relatively low-tax industries, energy and finance. But officials cautioned that other elements of the simplification plan might offset that added burden.

It is not hard to find the industries that would have the biggest tax increase, said another Treasury official, who asked that his name not be used: "You can tell by listening to the screams."