The federal government will spend $9.2 billion more in the fiscal year starting next October than the $440 billion proposed by President Ford yesterday, because laws exclude spending by some agencies from the formal budget.

As a result, according to the President, the deficit for fiscal 1978 should be $56.1 billion, not $47 billion.

In the current fiscal year, the official budget deficit is now projected to be $57.2 billion. But because the government will spend another $10.2 billion that does not show up on the budget, the actual difference between federal receipts and outlays is $68 billion.

Spending by these so-called "offbudget" agencies such as the Federal Financing Bank and the Postal Service fund does not differ "in nature, in effect or in concept from spending under similar programs included in the budget," according to the President's budget. But various laws require that the programs of nine federal agencies be excluded from the federal budget.

President Ford proposed that starting next year all off-budget agencies be included in the budget. A House Budget Committee study last year endorsed the idea as well.

Placing federal agencies off the budget runs counter to the idea of a "unified" federal budget which was adopted in 1969 to give taxpayers a fuller understanding of what the government is spending, the President noted.

In his budget proposals yesterday, he said that a unified budget "contributes to the rational establishment of priorities for allocating economic resources among alternative government programs because it subjects each program to the discipline of a budget process in which the benefits from additional (or lesser spending on one program are compared with the benefits of additional (or lesser) spending on all the others."

The first agency that was placed outside the budget - the Export-Import Bank in 1971 - was put back into the budget as of the beginning of the current fiscal year.

Except for the Postal Service fund, the Pension Benefit Guaranty Corp. and the Exchange Stabilization Fund, "the excluded outlays of the off-budget federal entities are incurred for carrying out loan programs," the President said.

The programs are similar to direct loan programs covered in the budget, yesterday's proposals said, and like "direct loans in the budget, the loans of the excluded programs are designed to allocate economic resources toward particular uses."

The Federal Financing Bank, which will spend $5.9 billion in fiscal 1978, is the biggest of the off-budget agencies. The Postal Service Fund will spend $1.8 billion and the Energy Independence Authority, which will start up during fiscal 1971, will spend $600 million, according to federal estimates.