Pursuant to a congressional request, GAO discussed: (1) the budget structure and current budgetary control regime; (2) the budget outlook, discretionary caps, and enforcement situation as the United States enters an era of projected unified budget surpluses; (3) potential implications of guaranteeing minimum spending levels on the discretionary side of the budget; and (4) the pay-as-you-go (PAYGO) side of the equation: (a) permanent appropriations; (b) mandatory trust funds; and (c) mandatory special funds.

GAO noted that: (1) the unified budget was adopted in 1969 as a way of capturing all federal receipts and expenditures; (2) Congress provides funds to agencies through budget accounts; (3) these accounts vary in their orientation, specificity, and size; (4) a relatively few large accounts are associated with three-quarters of budgetary resources, and the rest are comparatively quite small; (5) accounts may be oriented to program, process, organization, or object--and more than one orientation is likely to be found in a given agency; (6) the Budget Enforcement Act of 1990 (BEA) established a budgetary control regime that divided the budget into two major parts: (a) discretionary spending, defined as spending that stems from annual appropriation acts; and (b) direct spending, or spending that flows directly from authorizing legislation; (7) assuming that budget caps hold, after nearly 30 years of unified budget deficits, current projections are for surpluses lasting far into the future; (8) direct spending is still subject to the PAYGO rules, and discretionary spending is still subject to specified dollar caps; (9) discretionary caps were first imposed by BEA in 1990; (10) the structure of those caps--and so the constraints on trade-offs within the budget--has varied; (11) in the past, separate caps within the overall discretionary spending limit were designed to place firewalls between different areas of spending and to limit trade-offs to programs within each category; (12) like the caps, a guaranteed minimum funding level limits the range of trade-offs; (13) however, it also raises some additional issues; (14) its impact depends on the design of the guarantee; (15) providing guaranteed funding levels to any one activity in the budget protects that activity from competition with other areas for finite resources; (16) the mandatory spending part of the budget is comprised of spending that is not controlled through the appropriations process but instead is provided and controlled indirectly through other forms of legislation; and (17) there is no single rule for budgetary control of trust or special funds.