Appropriation bills are proposed laws that authorize the expenditure of government funds for specific purposes. They are also known as supply bills or spending bills. Appropriation bills are a key part of the annual budget process that lawmakers must enact to keep the government functioning regularly. Congress passes 12 annual appropriation acts, as well as supplemental appropriation acts, each year. These appropriation acts provide budget authority to obligate and expend funds from the U.S. Treasury for specific purposes.

The appropriation process begins with the adoption of a budget resolution that sets the top-line spending level for the upcoming fiscal year. The House and Senate Committees on Appropriations then divide that total among their 12 subcommittees. Guided by the subcommittee allocations, each subcommittee drafts its own appropriation bill. That process occurs in both the House and the Senate. Because the House and Senate Committees on Appropriations draft separate versions of the 12 appropriation bills for each fiscal year, there are often funding differences that must be worked out between the two bodies before the bills can be brought to the President for approval.

There are several kinds of appropriations, including annual or single-year appropriations, which are made for a specified fiscal year and are available for obligation only during the fiscal year for which made. Funds expire after one year and are no longer available to incur new obligations. Annual appropriations retain the fiscal year identity and remain available for recording, adjusting, and liquidating existing obligations and liabilities previously incurred. Expired appropriations are appropriations or fund accounts in which the balance is no longer available for incurring new obligations because the time available for incurring such obligations has expired. Funds may still be available for the recording and/or payment (liquidation) of obligations properly incurred.

In summary, appropriation bills are proposed laws that authorize the expenditure of government funds for specific purposes. They are a key part of the annual budget process that lawmakers must enact to keep the government functioning regularly. Congress passes 12 annual appropriation acts, as well as supplemental appropriation acts, each year. The appropriation process begins with the adoption of a budget resolution that sets the top-line spending level for the upcoming fiscal year. The House and Senate Committees on Appropriations then divide that total among their 12 subcommittees, and each subcommittee drafts its own appropriation bill.