GAO Glossary of Terms and Definitions (September 2005)
Shifting funds within an appropriation or fund account to use them for purposes other than those contemplated at the time of appropriation; it is the shifting of funds from one object class to another within an appropriation or from one program activity to another. While a transfer of funds involves shifting funds from one account to another, reprogramming involves shifting funds within an account. (For a distinction, see Transfer.)
Generally agencies may shift funds within an appropriation or fund account as part of their duty to manage their funds. Unlike transfers, agencies may reprogram without additional statutory authority. Nevertheless, reprogramming often involves some form of notification to the congressional appropriations committees, authorizing committees, or both. Sometimes committee oversight of reprogramming actions is prescribed by statute and requires formal notification of one or more committees before a reprogramming action may be implemented.