CONGRESS IS unprepared to make the spending cuts required to finance its proposed tax cut, but unwilling to admit it. To keep up the pretense of living within the necessary spending limits, it is resorting to gimmicks. The latest is to designate the census an emergency.

Never mind that the decennial head count is among the most routine of governmental functions, required by the Constitution, performed at 10-year intervals since 1790. Never mind that the budget rules say an emergency must be "sudden, quickly coming into being . . . unforeseen, unpredictable and unanticipated." What matters is that, if you call an expenditure an emergency, under the budget rules it doesn't count against that year's spending limits, the theory being that in the future it will go away.

In last year's end-of-session budget deal with the president, much use was made of the emergency designation, and Congress began this year by virtuously vowing never again. But that was before the process got underway. "This is a tough year for us, obviously," Rep. Harold Rogers, chairman of the House Appropriations subcommittee that funds the census, said a little sheepishly the other day.

The census is hardly the only example, though it may be the most ludicrous. Earlier this year, billions of dollars in routine defense expenditures, including even some military pay and pensions, were labeled "emergency," thereby moving them out from under the limits that would otherwise obtain. Before the year is out, billions in additional farm supports will likewise be given a pass. Congress, which normally favors the spending estimates of its own budget office over those of the president, this year has selectively adopted some of the president's because they suggest that spending will be less.

The Congressional Budget Office said the other day that, by its reckoning, the $14 billion surplus it had projected for next fiscal year in other than Social Security funds -- the money meant to finance the start-up of the tax cut Congress is in the process of voting -- has already been spent. These folks pledged they wouldn't touch the Social Security surplus, but they're already dipping into it to pay for spending bills, and that's before a tax cut takes effect. That's how the census will be paid for, if Mr. Rogers's subcommittee has its way. Most of the surplus that is supposed to pay for tax cuts is an illusion because it depends on spending cuts that aren't going to be made, nor for the most part should be. The census is an emergency only in the sense that, by double-counting dollars, they've made it one.