The project plan allows the project manager to communicate, control and manage the project and it is probably the most important thing a project manager can do to ensure the success of their project.

According to the PMBOK, a project plan is a formal approved document used to guide both project execution and project control. The primary uses of the project plan are to document planning assumptions and decisions, facilitate communication among stakeholders, and document approved scope, cost, and schedule baselines.

The detail of the project plan and its supporting documentation depends on the size of the project.

The project plan is a living document that changes as more information becomes available about the project, but the project baselines should only change when there has been an approved scope change.

A project plan typically includes the following:

• Project Charter
• Scope statement
• WBS
• Cost estimates
• Schedule (including the schedule baseline)
• Responsibility assignments
• Major milestones
• Required resources and their expected cost and / or effort
• Pending issues
• Risk management plan (key risks, constraints, assumptions, contingencies)
• Subsidiary management plans (scope, schedule, cost, quality, staffing, communication, procurement and risk management plans)
• Technical documentation
• Standards
• Assumptions

Resources
How to Create a Project Plan – Darwin Magazine