THERE'S SOMETHING you should know: The District hasn't had a real city budget for almost seven months. In most big cities, of course, you'd know it. But not in our town. The absence of the budget is of no apparent concern not only to the District government, but also to our Congressional overlords, as far as one can tell. Just the other day, as a matter of fact, Rep. William Natcher (D-Ky.), chairman of the House subcommittee on appropriations for the District, blithely convened a hearing on the 1979 budget even though there's still no 1978 budget in sight. The delay in congressional approval of this year's request is the result of an impasse between Rep. Natcher and Sen. Patrick Leahy (D-Vt.), chairman of the Senate Appropriations subcommittee, who cannot agree on one item: the proposed convention center. In October 1977 their standoff required Congress to pass a "continuing resolution," a legislative maneuver that forces the city to spend the same amount of money the same way it did last year - eliminating, at least for the moment, any new programs as well as any improvements to old ones.

Both the Congress and the city government rightly contend that the absence of this year's budget won't close down city government. But it assuredly is having, and will continue to have, and effect on a number of important activities. The Board of Elections and Ethics, for example, will still be able to hold the elections this fall, but it won't be able to provide for a voter-education drive or a registration campaign until the budget is approved. The public school system has been able to pay it in September if the continuing resolution is still in force. The "parking enforcement program" (the city's new method of collecting fines for traffic violations) is expected to bring in almost $20 million annually - but only if it gets started soon. The 1978 budget also provides for a number of construction projects that are relentlessly increasing in cost at the rate of 1 percent for every month of delay.That means that, as of right now, the University of the District of Columbia would have to add at least $1.6 million to the $57 million cost for its new Mt. Vernon campus; in the same way, congressional dallying has already added about $6 million to the cost of the new municipal office building, a new library, school renovation and other construction projects identified in this year's budget request.

Naturally, the local government has an explanation for not raising a ruckus about this sorry state of affairs. The mayor's representatives argue that the 1978 budget now before the subcommittees is so admirably "lean" and free of wasteful excess that not having access to the new money makes very little difference. But it does make a difference, of course, and not just with respect to specific programs and projects. One way it makes a big difference is that, without approval of the 1978 budget, it is impossible to calculate a firm base for the decisions that have to be made in the preparation of a 1979 budget.

What it really comes down to, if you ask us, is that the city doesn't want to antagonize either Mr. Natcher, who is defending the convention center, or Mr. Leahy, who is opposing it. There was a time when we had some sympathy for that strategy, on the assumption that the delay on the budget might force some new thinking on the convention center. But that hasn't happened. And with each passing day it seems less likely to happen.

So we think Mr. Natcher should take Mr. Leahy up on his offer to convene the House and Senate subcommittees and try to reach speedy agreement on all items in the 1978 budget except the convention center. That would remove Mayor Washington's excuse that it is a failure to act on the budget, rather than a failure to agree on the convention center, that are going to have to be made on the proposed convention center if the city is not to muddle along with a continuing resolution indefinitely.