Congress gave final approval yesterday to a government funding resolution for the rest of this fiscal year after the Senate, flinching at the prospect of self-sacrifice, dropped an effort to repeal the tax break that members of Congress voted themselves last year.

Voting 81 to 18, the Senate approved emergency funding for government departments and agencies for which regular appropriations bills have not been passed and sent the measure to President Reagan, who signed it well in advance of the midnight deadline for passage.

The Senate action allows seven departments and many related agencies, which had prepared for a possible shutdown today for lack of funds, to stay in business. The new funding authority lasts through the end of fiscal 1982 on Sept. 30.

The House had previously approved the funding measure without extraneous amendments, but the Senate had not been able to resist the temptation to dress it up a little, and wound up in a binge of pay and benefit cutting that threatened to get out of control.

At one point the Senate had voted not only to repeal last year's tax break but also, as part of the same amendment, to cut congressional pay by 10 percent and require members of Congress to disclose their tax returns each year.

This was clearly more than the Senate had bargained for Tuesday when it first indicated it would try to make some political hay out of giving up the tax break. So, after repeatedly spurning earlier leadership appeals for resistance to all amendments, the Senate went along with a point of order by Appropriations Committee Chairman Mark O. Hatfield (R-Ore.) that had the effect of derailing all the pay and tax provisions.

With that hurdle cleared, Sen. Jesse Helms (R-N.C.), who had been ready with an amendment aimed at forcing the House to act on antibusing legislation, backed off. So did Democrats, who were reportedly ready with some 200 possible amendments that a Republican leadership aide ruefully characterized as "their whole legislative agenda for the year."

As the day started, it appeared that Sen. William L. Armstrong (R-Colo.) might win approval for his amendment to drop the tax break under which members can now deduct $75 a day from their taxable income for Washington living expenses, and return instead to the old $3,000 annual limit on tax deductions for Washington living expenses.

If he succeeded, Senate leaders feared "the floodgates would open" to more amendments, as Hatfield put it, and jeopardize House-Senate accord on the bill by midnight. Moreover, Hatfield warned his rebellious colleagues, the House, which has been especially keen on the tax break, might retaliate by trying to take away the generous ceiling on honorariums from speechmaking that senators also voted themselves last year.

So Sen. Ted Stevens (R-Alaska), who bitterly opposed Armstrong's proposal, led an effort to load up Armstrong's amendment with so many other potentially expensive gestures of self-sacrifice that the measure would eventually collapse of its own weight. And Senate leaders arranged the crucial votes to come on relatively arcane points of order, making it easier for nervous lawmakers to hide their votes in favor of keeping the tax breaks.

On the first point of order, Hatfield failed to kill the tax break repealer, 57 to 41. However, after the 10 percent pay cut was added to Armstrong's proposal, Hatfield won, 51 to 48.

But even that was a close call, with Stevens and Majority Leader Howard H. Baker Jr. (R-Tenn.) working on the floor to switch votes at the last minute. Sen. John W. Warner (R-Va.) was among those who switched. The rest of the Washington-area delegation voted both times to repeal the tax break.

Both the tax break and antibusing issues appeared certain to come up again, however. In an attempt to get Armstrong to back off, Senate Finance Committee Chairman Robert J. Dole (R-Kan.), along with the ranking committee Democrat, Russell B. Long (La.), pledged to find another vehicle for the tax break repealer. And Helms said he would tack his antibusing measure to the debt ceiling extension bill that Congress must approve later this spring if the House hasn't acted on Helms' measure in the meantime.

At that time, said Helms, the debate will "like Tennyson's brook roll on and on." Thankful even for the brief respite, Baker responded, "I'll worry about that next week."

Meanwhile, both the Budget and Finance committees of the Senate marked time in developing alternatives to President Reagan's budget, apparently deciding to wait until after the upcoming Easter recess to begin work on specifics.

But three Democrats on the Budget Committee--Sens. Daniel Patrick Moynihan (N.Y.), Donald W. Riegle Jr. (Mich.) and Jim Sasser (Tenn.)--proposed yet another budget alternative, focusing on getting the Federal Reserve Board to ease up on the money supply in order to bring down interest rates.

The three proposed repeal of indexing tax rates to inflation after 1984 but would not change Reagan's individual tax cuts. They would cut back the growth in defense spending but would not trim cost-of-living increases for Social Security and other benefit programs.