SEN. BILL BRADLEY and Rep. Richard Gephardt have introduced a bill that would make the tax law simpler and fairer. The measure will not appeal to those lobbies and their congressional advocates who have so carefully crafted each subsidy and incentive now embedded in the tax code. But it should be enormously gratifying to the great majority of taxpayers who justifiably suspect that the complexity of the system serves little purpose beyond fattening the pocketbooks of tax lawyers and accountants.

Like the "flat tax" plans that have recently gained currency, the Bradley-Gephardt plan would raise the same amount of revenue with much lower tax rates. This would be done by eliminating exemptions and deductions that currently shield much income from taxation. But the plan also addresses concerns raised about flat-tax plans by preserving a few highly popular deductions. By keeping a limited amount of progressivity in the individual rate schedule, it would also preserve the current distribution of the tax burden among income classes.

For individual taxpayers, a basic tax rate of 14 percent would apply. In computing this basic tax, the filer could claim personal exemptions and either a standard deduction or a few itemized deductions including home mortgage interest and charitable contributions. Higher-income taxpayers would also pay surtaxes on income above a certain amount, but the total tax rate would not exceed 30 percent.

Corporate tax rates would also be reduced to 30 percent, and a vast array of tax breaks would be eliminated. The plan would revise and simplify the current method for depreciating equipment and buildings. Because depreciation would relate more closely to the actual useful life of investments, the tax incentives that currently distort production decisions would be reduced.

With respect to the general flow of recent tax policy, the Bradley-Gephardt plan is clearly swimming upstream. Republicans and Democrats alike pay lip service to the benefits of deregulation. But both parties--with the encouragement of corporations and upper-bracket individuals who are shy about accepting front-door favors--have manipulated the tax code to encourage or discourage certain behavior. Most of these tax incentives, if they work at all, are quickly outmoded or simply cancel out favors earlier granted to some competitor.

But Congress will find it hard to kick the tax- break habit--and the hefty campaign contributions it brings. Presidential aspirants from Messrs. Bradley and Gephardt's own party are now out on the hustings promising new tax benefits to resuscitate old industries and nurture the new. The only possible check on this tendency would be for thoughtful individuals and businesses to start telling their congressmen that they don't mind paying taxes if they are simple and low, and that they don't need the tax code to tell them how to spend their money.