AS EVERY congressman knows, procedure controls substance. The House is now going to be dealing simultaneously with three crucial fiscal bills -- the budget, the income tax cut and the Social Security revisions. Some of this year's procedures are unfamiliar, and the play among these bills will not be simple, so it's useful exercise to sketch out the schedule as it now seems to stand.

The budget resolution, passed this week, contains a drastic application of the 1974 Budget Act that has never been attempted before. With the help of conservative Democrats, you will recall, the Republican minority succeeded in committing the House to President Reagan's budget. The resolution not only assigned budget cuts to each legislative committee but -- this part is new -- required them to report those cuts back to the Budget Committee by June 12.

When the Ways and Means Committee voted on Tuesday to reduce a series of programs by $9 billion a year, that's what it was doing -- conforming to the budget resolution. What if a committee refuses, as the Education and Labor Committee may do? Then the Budget Committee itself has the power and the obligation to impose the required cuts. In each case, incidentally, it is not merely the appropriation but the basic authorizing legislation that is being amended downward.

The Budget Committee is then to take all of those spending amendments, roll them into one big bill, and bring it to the floor sometime, according to present plan, in late June. Among the Democrats there's a debate whether to permit further amendments on the floor. That involves the Democratic leadership's strategy in dealing with the rebels who voted with the Republicans last time. The outcome has implications not only for the budget but also for the Democratic Party.

The tax bill, under a firm bipartisan agreement, is to come up only after that vote on the budget -- to avoid the temptation to pass tax cuts without the matching spending cuts. But the agreement is becoming superfluous, as the negotiations with the administration over a tax compromise introduce new dealys. The Ways and Means Committee has suggested that it would sit down to write its version of the bill in the first week of June, with a floor vote perhaps at the end of the month and Senate action in July. The leadership still says that it hopes to send the tax bill to the president before the August recess, but that looks unlikely.

In Spetember, Congress will return to vote on the second budget resolution -- in theory hardly more than a ratification of the first one. But the first one is based on exceedingly optimistic economic assumptions that will probably be contradicted by the summer's statistics. Since the second resolution sets legal limits to spending and the federal deficit, Congress may well have to make a choice between raising those limits or finding further budget cuts in the fall.

It's not yet clear where Social Security fits into this timetable. The administration would like to keep the pensions, with their enormous emotional freight, separate from the other fiscal issues. But Congress knows that they aren't really separable. Social Security is nearly one-fourth of the total federal budget, after all, and the Social Security payroll tax is second only to the individual income tax among the government's revenue raisers. It's not only fiscal policy that is being profoundly changed as these bills go through but the House's procedures for making that policy, and perhaps the political structure of the House itself.