The federal budget deficit for fiscal 1984 was $175.342 billion, $1 billion higher than the Reagan administration estimated in its mid-session review in August, the Treasury Department reported yesterday.

The deficit was estimated in August to be $174.303 billion. Last year it was $195.354 billion.

During the year ended Sept. 30, the government collected $666.5 billion in revenue and had $841.8 billion in on-budget outlays. In August, the government had estimated receipts to be $670.7 billion and on-budget outlays of $845.0 billion, Treasury said.

The decrease in revenue resulted from collections of individual income taxes that were $3.6 billion below what had been expected. Lower-than-anticipated nominal incomes were blamed for the shortfall, said a joint statement from the Treasury Department and the Office of Management and Budget. Individual income tax receipts were $295.955 billion, compared with the $299.525 billion estimated in August.

In addition, corporate income taxes, "primarily reflecting lower corporate profits," were $2.1 billion lower than earlier projected, the statement said. Those tax receipts were $56.893 billion, compared with the earlier estimate of $59.016 billion. Other receipts were $1.5 billion higher.

Total outlays were lower than expected because of a shortfall in defense military spending. Defense military spending was $220.805 billion, compared with the expected $227.0 billion.

Interest on the debt was $1.7 billion above the August estimate because of higher-than-anticipated interest rates, changes in Treasury borrowing and a technical estimating error, Treasury said.

Including off-budget items, the total deficit was $185.3 billion for fiscal 1984.