The Budget of the United States Government is the President's proposal to the U.S. Congress which recommends funding levels for the federal government for the next fiscal year, beginning October 1. Budget and appropriations are usually referred to by the fiscal year (FY) to which they apply (i.e. fiscal year 2010 is FY10).
Each year, the President of the United States submits his budget request to Congress for the following fiscal year as required by the Budget and Accounting Act of 1921. Typically, presidents submit budgets on the first Monday in February. The budget submission is sometimes delayed, however, in some new presidents' first year.
After Congress receives the President’s budget proposal, it begins its own budgetary process. Congressional decisions are governed by rules and legislation regarding the federal budget process. Budget committees set spending limits for the various House and Senate committees. Budget resolutions reflect spending priorities of Congress, and will usually differ from funding levels in the president's budget. (The president, however, retains substantial influence over the budget process through his veto power and through his allies in Congress.) The Congressional Budget must be passed by both the House and Senate, but is not subject to Presidential signature. Once passed by both chambers, it has the force and effect of law.
The budget guides the work of the House and Senate Appropriations committees, which then approve individual appropriations bills to allocate funding to various federal agencies and programs. Federal agencies cannot spend money unless funds are authorized and appropriated.
The House and Senate Appropriations Committees currently have 12 subcommittees, which are responsible for drafting the 12 regular appropriations bills that determine amounts of discretionary spending for various federal programs.
Appropriations bills must pass both the House and Senate and then be signed by the president in order to give federal agencies legal authority to spend. In many recent years, legislators have sometimes adopted a practice of combining several regular appropriations bills have into an "omnibus" bill. This allows one vote to be taken on the whole package, rather than several separate votes.
In addition, the president may request and the Congress may pass supplemental appropriations bills as needed. Congress may also pass bills for emergency appropriations. Spending that is deemed an "emergency" is exempt from certain Congressional budget enforcement rules. Funds for disaster relief have sometimes come from supplemental appropriations, such as after Hurricane Katrina. In other cases, funds included in emergency supplemental appropriations bills support activities not obviously related to actual emergencies, but to urgent needs of the federal government.
After Congress approves an appropriations bill, it is sent to the President, who may sign it into law, or may veto it. A vetoed bill is sent back to Congress, which can pass it into law with a two-thirds majority vote in each chamber.