Milestones are a way to monitor the project's progress. They usually coincide with completion of specific aspects of a project that might be logical sub-steps in completing the project as a whole.

You can set milestones and project checkpoints to coincide with the sequence of the deliverables or points of payment within a project. The employer is responsible for creating the milestones previously agreed by both parties.

As the project progresses the employer is also responsible for closing milestones until the final closure of the project. Including some appropriate milestones is recommended for most projects.