A Summary Plan Description (SPD) is a document that participants or beneficiaries of any ERISA-covered retirement or health plan are entitled to receive. The summary plan description is an important document that tells participants what the plan provides and how it operates. It provides information on when an employee can begin to participate in the plan, how service and benefits are calculated, when benefits becomes vested, when and in what form benefits are paid, and how to file a claim for benefits. The plan administrator is legally obligated to provide to participants, free of charge, the SPD. If a plan is changed, participants must be informed, either through a revised summary plan description, or in a separate document, called a summary of material modifications, which also must be given to participants free of charge.