AS USUAL at this time of year, the congressional budget process looks as though it is falling apart. The House doesn't seem to have a majority in favor of anything, and it's already a week over the deadline for its final budget resolution. The Senate has just overridden its Budget Committee on defense spending, and seems to be heading into a collision with the House.

But, in fact, the new and reformed budget process, now in its fourth year, is working well. It is maintaining discipline on the committees, and it is forcing the central questions of policy to explicit votes on the floor.This year the central questions are defense spending and tax cuts, and so far all of the decisions -- in the Senate to raise the defense budget, and in both houses to postpone the tax cuts -- have been the right ones.

Until 1975, Congress parceled the budget out to the committees and never attempted to put it back together. In the Senate this year, several of the more powerful committees engaged in a rebellion to recover some of their lost discretion. They deliberately and unrepentantly overran the limits that the Senate as a whole had voted last spring. But the Budget Committee courageously stood its ground against all comers and, in long Democratic Party caucuses last week, forced the others to retreat. The Agriculture and Veterans Affairs committees took appeals to the floor, and lost. The Budget Act of 1974 is that rarest of birds, a reform that actually works.

Republicans in both houses have been pushing tax reduction. But any significant drop in taxes, in the present circumstances, would be inflationary if it were not balanced by a similar drop in spending. The Republican sponsors of these plans said that, they favored less spending. But that would be neither desirable nor, as a practical matter, possible in a year when unemployment will be rising. There's an interesting and faintly comic reversal of roles here, with the Republicans shouting for tax cuts to generate growth while the Democrats grimly stick, with well justified caution, the the stony paths of fiscal rectitude.

The increase in the defense budget was a considered choice by the Senate, and a wise one. The country's commitment to an annual 3 percent increase above the inflation rate is a longstanding one, and has to be kept. There's no joy in raising defense outlays, but neither are they an intolerable burden. In proportion to either the total federal budget or the country's entire economic output, defense spending next year will be substantially less than it was before the Vietnam War. Next year, with the Senate's increase, spending for defense would be about 5.2 percent of the gross national product. In 1964, it was 8 percent. It would be pleasanter if the Soviet Union were exercising restraint in the deployment of its weapons, permitting relaxation here. But, unfortunately, that is not the world in which we are all living.