"Authorization laws have two basic purposes. They establish, continue, or modify federal programs, and they are a prerequisite under House and Senate rules (and sometimes under statute) for the Congress to appropriate budget authority for programs.

Some authorization laws provide spending directly. In fact, well over half of federal spending now goes to programs for which the authorizing legislation itself creates budget authority. Such spending is referred to as direct, or mandatory, spending. It includes funding for most major entitlement programs. (Some entitlements are funded in annual appropriation acts, but the amounts provided are controlled by the authorization law that established the entitlement.) The authorization laws that provide direct spending are typically permanent, but some major direct spending programs, such as the Food Stamp program, require periodic renewal.

Discretionary spending, which is provided in the 13 appropriation acts, now makes up only about one-third of all federal expenditures. For discretionary spending, the role of the authorizing committees is to enact legislation that serves as the basis for operating a program and that provides guidance to the Appropriations Committees as to an appropriate level of funding for the program. That guidance typically is expressed in terms of an authorization of appropriations. Such authorizations are provided either as specific dollar amounts (definite authorizations) or "such sums as are necessary" (indefinite authorizations).

In addition, authorizations may be permanent and remain in effect until changed by the Congress, or they may cover only specific fiscal years. Authorizations that are limited in duration may be annual (pertaining to one fiscal year) or multiyear (pertaining to two, five, or any number of specific fiscal years). When such an authorization expires, the Congress may choose to extend the life of a program by passing legislation commonly referred to as a reauthorization. Unless the underlying law expressly prohibits it, the Congress may also extend a program simply by providing new appropriations. Appropriations made available for a program after its authorization has expired are called "unauthorized appropriations."

Longstanding rules of the House allow a point of order to be raised against an appropriation that is unauthorized. During initial consideration of a bill in the House (which by precedent originates appropriation bills), unauthorized appropriations are sometimes dropped from the bill. However, the House Committee on Rules typically grants waivers for unauthorized appropriations that are contained in a conference agreement. In the Senate, there is a more limited prohibition against considering unauthorized appropriations.

Both House and Senate rules require that when the Committees on Appropriations report a bill, they list in their respective committee reports any programs funded in the bill that lack an authorization. The information in the committee reports, however, differs somewhat from the information shown in this report. This report covers programs that at one time had an explicit authorization that either has expired or will expire. Unlike the lists shown in the Appropriations Committee reports, this report does not include programs for which the Congress has never provided authorizations of appropriations. For example, some Treasury Department programs have never received explicit authorizations of appropriations. They receive appropriations nonetheless because the authority to obligate and spend funds is considered "organic"--inherent in the underlying legislation or executive action that originally empowered the Treasury to perform particular functions.

As mentioned above, many laws establish programs with authorizations of discretionary appropriations that do not expire. Both the Appropriations Committee reports and this CBO report exclude programs with that type of authorization because its effect is permanent."

(Excerpted from a Congressional Budget Office report -- Copy of document on CBO Web Site)