Lost in the drive to enact a new minimum tax on corporations and individuals is a little-noted fact: Such taxes already exist and have proved virtually toothless.

Minimum taxes on the incomes of individuals and corporations were first enacted in 1969 amid disclosures that some wealthy individuals and firms legally escaped taxation.

The taxes have been amended three times since then, but still cover only 0.3 percent of taxpaying corporations and 0.1 percent of taxpaying individuals. The total revenue is $500 million a year.

The current minimum tax -- 15 percent on corporations and 20 percent on individuals -- has proved to be ineffective, in part because it doesn't cover many preferences built into the tax code.

"It seems to be just another indication of how difficult things become when you get into a philosophy of, here's a ball, don't bounce it," said Joseph J. Minarik of the Urban Institute. "You put the preferences into the law and then decide to limit their use."

Analysts say the minimum tax on individuals has more bite than the corporate minimum tax. It is an "alternative tax," of the kind now being considered in Congress and by the Reagan administration as part of its revised tax-simplification proposal. Essentially, taxpayers figure their tax in two ways: the regular way and then without using certain deductions. They pay whichever is greater.

Even so, Internal Revenue Service figures show 447 individual returns with adjusted gross incomes of more than $200,000 had no tax liability in 1983.

The current corporate minimum tax is regarded as almost useless. Businesses add to their tax bill a percentage of the value of their deductions. But the list of preferences that must be added back is very short, and thousands of corporations manage to use such tax benefits as the foreign tax credit and the investment tax credit to negate their tax liability.

Even President Reagan tried to do something about this problem during his first term.

In his 1982 State of the Union address, Reagan pledged to "plug unwarranted tax loopholes." His Treasury Department, fretting about profitable corporations paying little or no income taxes, proposed a broad 15 percent minimum levy on business.

It all came to naught. The proposal, cut to ribbons by heavy business lobbying, never was sent to Congress and almost none of it showed up in the tax bill passed later that year.

Treasury estimated in 1982 when it proposed the minimum tax that it would apply to about 90,000 profitable corporations that paid little or no tax. The 15 percent corporate minimum levy endorsed by Reagan would have limited such widespread preferences as accelerated depreciation and oil exploration expenses, and raised taxes on such relatively low-tax industries as financial institutions and real estate.

"We started dropping stuff as the businesses came in to complain," said Mary Hevener, who as a Treasury Department attorney in 1982 drafted much of the minimum-tax proposal. "By June we had dropped so much, the whole thing was dead. We were back to where we started."