The White House won't say whether President Carter will sign or veto legislation that would eliminate a retroactive 1976 tax slapped on the sick and disability income of more than 1.5 million taxpayers.

Both the Senate and House approved bills that would have restored the tax relief break for the 1976 year, permitting individuals to exclude up to $100 a week of sick or disability pay from their 1976 federal taxes. But a last minute snarl developed in the Senate when Finance Committee Chairman Russell Long (R-La.) warned that Carter might veto the plan. That kept Congress from sending a compromise bill to the President before the April 15 tax filing deadline.

More than a million taxpayers who had not budgeted for the total extra $300 million tax bite on sick and disability pay had to come up with the additional money for IRS. Now they are looking for legislative relief that will permit them to file for refunds on the extra tax paid.

The Senate and House each voted, unanimously to give the tax break, by changing the effective date of the tax law from Jan. 1, 1976 to Jan. 1, 1977. The hangup initially came from unrelated amendments that were added to the bill. When the legislation came back to the Senate, Long warned it could face problems with the White House. The Senate adjourned without taking final action.

Sen. Robert Dole (R-Kan.) and Rep. Bob Daniel (R-Va.) wrote President Carter asking him to endorse their bills so the tax break could be settled quickly. More than two weeks went by before they got a noncommital reply from a White House aide saying the President was aware of the issue, and that it had been referred to another aide for consideration.

Meantime, Sen. Long has appointed six conferees (including himself) to meet with the House on the tax problem. Ways and Means Committee Chairman Al Ullman (D-Ore.) is expected to name House members soon. The meeting could come next week.

Insides expect the conferees will work up a compromise - including the 1976 tax break - that the full Senate and House will again approve. The question is whether the President will sign it (the Treasuru Department doesn't want to have to give back more than $300 million in refunds). The White House hasn't given any signal yet.

Vernon D. (Mike) Acree will retire at the end of the month, capping a 40-year career from messenger to commissioner of Customs. He's considered one of the best, and is one of the last of the up-from-the-ranks generation that has produced some of the government's top executives.

Walter Wurfel, deputy presidential press secretary, is the April 28 speaker at the Government Communicators Flagship luncheon. Call 524-9400, ext. 719 on Monday for reservations.