A change request can de defined as any request that is submitted to whatever change control board or decision making group has been implemented. These change requests can consist of changes which range from minor changes to significant changes that drastically alter the project, however, typically formal change requests involve more significant changes and the less impactful changes are made at the project management level. A typical change request can request a change to a number of project areas including requests to expand or reduce the scope of the project, requests to modify policies, procedures, plans, or processes, requests to modify expenditures, and requests to update of modify schedules. Change requests can be made directly or indirectly, and can be initiated internally or externally. One constant throughout most change request processes is that change request must be made formally, via a written proposal or request form typically, and that changes are not to be implemented until they are formally approved.
This term is defined in the 3rd and the 4th edition of the PMBOK.