The Treasury Department is considering a minimum tax on corporations and possibly on individuals as part of its revised tax-simplification plan, administration officials said yesterday.

The minimum-tax concept is gaining popularity in Congress, and some legislators, especially Democrats, want to use the tax to raise revenue. Administration analysts want to use revenue from any minimum tax to offset a lowering of tax rates.

Treasury Secretary James A. Baker III has given President Reagan and Vice President Bush three briefings on changes he recommends in the Treasury tax proposal, originally made last November when Donald T. Regan was Treasury secretary.

Baker is believed to have recommended modifying proposed cutbacks in fringe benefits, business depreciation and contributions to Individual Retirement Accounts, according to administration, congressional and private sources.

Reagan will not decide on a package to present to Congress before he returns from Europe next weekend.

A minimum tax would have significant implications for the shape of the final package. Officials said it would be a signal that political pressure against abolishing certain loopholes had prevailed.

A minimum tax generally limits the extent to which particular tax preferences can be used.

Among the preferences that sources suggested could be preserved under a minimum tax are fast writeoffs for oil and gas drilling costs, preferential tax rates for timber and perhaps certain farm provisions, all slated for oblivion under the original tax-simplification proposals.

It is not clear whether the minimum tax would apply to individuals as well as corporations.

The Senate Thursday night adopted a nonbinding resolution supporting the concept of a minimum tax as it was considering the budget. The resolution specified that revenue should be used to lower tax rates, not reduce the deficit.

However, Sen. Lawton Chiles (D-Fla.), ranking Democrat on the Senate Budget Committee, said he plans to offer a substitute budget resolution that would call for a minimum tax to reduce the deficit. The Chiles package would include about $68 billion in revenue increases and $160 billion in spending cuts over the next three years.

In the House, such Democrats as Majority Leader James C. Wright (Tex.), Marty Russo (Ill.) and Charles E. Schumer (N.Y.) are pushing a minimum tax. Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.) has warned, however, that a minimum tax could be a "cop-out" if it is not coupled with broader tax revision.

Baker is said to have tentatively decided on these alterations in the original Treasury plan:

* More fringe benefits would be exempt from taxation. Congressional sources said a likely option is to tax the first $100 in employer-paid health premiums per month, rather than taxing everything over $175 per family as the first plan suggested. Company-sponsored cash retirement savings accounts, known as 401 (k) plans, would be limited but not abolished.

* Capital gains -- profits on the sale of an asset -- would be taxed at a lower rate, rather than as ordinary income. But the value of assets would not be adjusted to account for inflation and the definition of capital assets would be narrowed, perhaps including only stock equities.

* The top rate for individuals would be cut to 35 percent from the current 50 percent as originally proposed. The corporate rate could be a few points higher than the 33 percent first suggested. The current top corporate rate is 46 percent. The department also is expected to recommend retaining graduated rates for small companies, something the original Treasury plan would have abolished.

* Charitable contributions would either remain fully deductible, as under current law, or would be deductible at amounts above 1 percent of adjusted gross income. The earlier plan set a ceiling of 2 percent.

* The personal exemption, slated to go to $1,090 next year, would be increased to $1,800 rather than the $2,000 first proposed. The Treasury gains about $5 billion with each $100 decrease in the personal exemption. * Permissible contributions to tax-deferred Individual Retirement Accounts would be retained at their current level of $2,000 rather than raised to $2,500.

* Business depreciation writeoffs would be more generous than the proposed system but less generous than current law. The method by which the Treasury would strike a middle ground is not known, but is expected to lump the tax benefits in earlier years as the current system does. The investment tax credit still is expected to be terminated.