Negotiators are trying to reach a compromise on sharply differing tax bills passed by the House and Senate, one containing a "taxpayers' bill of rights" and the other offering relief for 20 million owners of mutual funds.

The Senate bill, which was approved Tuesday night on an 87-1 vote, would cut selected taxes by an estimated $3 billion over three years and, to avoid worsening the deficit, boost other taxes by the same amount. The House bill, passed 380-25 on Aug. 4, has a $7.5 billion price tag.Far more provisions are identical in both bills. Both would correct hundreds of technical errors in the 1986 tax overhaul; extend several expiring tax benefits; relieve farmers from paying the federal diesel tax on fuel for off-road use, and raise some taxes to pay for the benefits.

The tax bill and a comprehensive plan for fighting drug abuse are the only major pieces of legislation standing in the way of adjournment of the 100th Congress, as early as this weekend.

"All of us realize the more revenue we have in this bill, the less likely the president is to sign it," said Sen. Max Baucus, D-Mont., manager of the Senate tax measure. Thus, the Senate will try to hold down the cost and House negotiators will be pushing for senators to accept some new provisions.

Sen. Bill Bradley, D-N.J., cast the only vote against the Senate bill. A principal architect of the 1986 tax changes, Bradley has argued against undue tampering with the new system, saying it should not be riddled with special-interest provisions.

Not voting on the 87-1 Senate vote that passed the tax bill were: Sens. Lloyd Bentsen, D-Texas; David Boren, D-Okla.; Lawton Chiles, D-Fla.; Thad Cochran, R-Miss.; Daniel Evans, R-Wash.; Phil Gramm, R-Texas; David Karnes, R-Neb.; Frank Lautenberg, D-N.J.; Richard Lugar, R-Ind.; Dan Quayle, R-Ind.; Malcolm Wallop, R-Wyo., and Pete Wilson, R-Calif.

Both the House and Senate bills would extend several expiring tax benefits, with the Senate opting for a shorter extension in order to reduce the cost. These include a credit for business research, an exclusion for workers' employer-financed educational assistance, and a tax break for low-income first-time home buyers.

The Senate bill, but not the House, would set up a "bill of rights" for taxpayers who are the subject of collection or other enforcement efforts by the IRS.

The agency would have to inform taxpayers fully of their rights at the time an action is launched and would be barred from promoting employees on the basis of how much they collect.