The United States government woke up this morning to a brand new fiscal year. According to civics books, that means the government starts work under a brand new budget today.

Except it's not that simple. The government doesn't have a budget for the new year, Fiscal Year 1982, because Congress hasn't finished one yet. According to civics books, that means Congress will pass a kind of temporary budget--a "continuing resolution"--until it gets around to passing the 13 annual appropriations bills that make up the budget.

Except it's not that simple. Congress was considering a "continuing resolution" last night that will allow government agencies to keep working for the next month or so. But if recent history is a guide, Congress may never get around to passing all the appropriations bills for fiscal 1982. When fiscal year 1981 wore down to its end last night, there were still five appropriations that had never been enacted. That meant about five-thirteenths of the government operated all last fiscal year on "temporary" spending authority.

This year, perhaps, Congress could do better. There are still 12 months left for it to pass appropriations bills for fiscal 1982, and with concentrated effort that could be done.

Except it's not that simple. In January, the admninistration will present Congress a whole new budget package--for fiscal 1983--and the members will have to deal with that while they're still working through the spending plan for this year.

So how can anybody know what the government's budget will be for the new year starting today? You could add the spending levels in the appropriations bills that eventually do pass, and the levels in the "continuing resolutions" enacted to fill the gaps where there is no appropriation, and come up with a total spending figure.

Except it's not that simple. In addition to the spending reflected in the budget bills, the government will spend additional sums--probably $30 billion or more next year--on a category of programs referred to as "off-budget items."

So maybe you could just add up all the "on-budget" and "off-budget" items and get a total for the new year's real federal budget.

Except it's not that simple. In addition to all the activities it pursues by spending money, the government also carries out various programs by lending money or by guaranteeing private loans. These government credit programs will total about $139 billion in the year that starts today, but won't show up in the budget.

In short, it is not simple.

Things, however, were not always so complicated.

During the country's first 50 years, things were so (relatively) simple that the agencies didn't even need a special fiscal year. Congress convened in the first week of December and passed a budget for the coming year in time for the real New Year's Day.

But as government got bigger and Congress got more talkative, it became harder to squeeze the budget debate into three weeks. In 1842, Congress adopted a new fiscal year beginning July 1--a date that allowed more than six months to pass the budget.

The July 1 New Year's Day lasted until calendar year 1976, when Congress gave itself additional budget time by establishing the current fiscal year of Oct. 1 to Sept. 30. As the fiscal 1981 experience shows, though, the additional three months did not help much; Congress finished only eight of the 13 appropriations bills last year, its worst record ever.

It should be noted, though, that one apparently confusing aspect of all this fiscal flummery is quite simple. There is no trick to figuring out what the fiscal year is at any given time. The number of the fiscal year is the number of the calendar New Year that falls during the fiscal year--e.g., the fiscal year that runs from Oct. 1, 1982, to Sept. 30, 1983, will be fiscal 1983.