As if you didn't know, last midnight (grumble, grumble) was the deadline for filing federal income tax returns (.!%&.%), and the National Taxpayers Union couldn't let it go by without a grumble-grumble-@%&@%..

The NTU, an organization of 60,000 members who are fed up with high taxes, used the occasion to trot out a computer study of the most frugal and most profligate spenders in the Congress.

NTU reviewed more than 100 authorization and appropriation votes, plus votes on amendments in 1977 that would increase or reduce federal spending, then assigned scores to each legislator.

And now, the envelopes, please . . .

The biggest spender in the Senate was Sen. Daniel Inouye (D-Hawaii), with a score of 16 out of a possible 100. (The lower the score the less frugal the member.) The biggest House spender was Rep. Claude Pepper (D-Fla.), with a 9.

The most frugal senator was Harry F. Byrd Jr. (Ind.-Va.), with a 58, and the House's leading skinflint was Rep. Philip Crane (R-Ill.), with an 82.

James Davidson, NTU chairman, [WORD ILLEGIBLE] at a press conference that the [WORD ILLEGIBLE] suggests whether legislators [WORD ILLEGIBLE] able to set priorities to "avoid [WORD ILLEGIBLE] things as $60 billion federal [WORD ILLEGIBLE] deficits."

Some of the winners of the most [WORD ILLEGIBLE] prizes took part in the event, receiving plaques and decrying excessive authorizations and appropriations by their brethren.

Said Sen. Byrd:

"I don't know anything more important to the average citizen . . . To me, it is horrifying - the waste, squandering and mismanagement of tax money."

These were the other leaders identified by NTU:

SENATE - The biggest spenders were Inouye; the late Lee Metcalf (D-Mont.), 17) Gary Hart (D-Colo.), 18; Mike Gravel (D-Alaska), Abraham Ribicoff (D-Conn.), and Jim Sasser (D-Tenn.) 20.

The most frugal were Bryd; William Roth (R-Del.), 57; Jesse Helms (R-N.C.), 56; William Proxmire (D-Wis.), 53; Paul Laxalt (R-Nev.) and William Scott (R-Va.), 51, and Orrinn Hatch (R-Utah), 50.

HOUSE - Leading spenders were Pepper; Daniel Flood (D-Pa.), 11; John M. Murphy (DN.Y.), 12; and James A. Burke (DMass.), 14. The most frugal were Crane; William Armstrong (R-Colo.), 74; and James Collins (R-Tex.), 72.

Inouye responded, "I will defend all my votes in the Senate to my constitutency. I am not embarrassed at all about my vote record."