PRINCE2: Stage, Exception and Boundary

PRINCE2 is a structured and adaptable project management method for planning, managing and controlling any type or size of project.

Stage: At any one time, a Project Manager (PM) manages one section of a project, called stage. At the end of the stage, the project Board reviews the status of the
project to date and decides whether to continue to the next stage

Exception: An exception is a situation where it is forecast that there will be a cost or schedule deviation beyond the project's planned tolerance levels set by the Project
Board. The Project Manager prepares an Exception Report, which describes the exception situation.

Boundary: The term boundary is used in the context of Managing Stage Boundaries, a PRINCE2 process. PRINCE2 provides a mechanism for defining the boundary of a project
and its relationship to other projects. in defining the boundary of a project, as with a stage, the emphasis is always on the products that the project is required to deliver.
As a project nears a stage boundary, or end of a stage, the Project Board, assesses the information produced from the current stage and makes a key decision on whether
to continue with the project or not.