What is Retention Period?

Legal Definition
The retention period of information is an aspect of records and information management (RIM) and the records life cycle. It identifies the duration of time for which the information should be maintained or "retained", irrespective of format (paper, electronic, or other). Retention periods vary on different types of information, based on content and a variety of other factors including: internal organizational need, regulatory requirements for inspection or audit, legal statutes of limitation, involvement in litigation, taxation and financial reporting needs, as well as other factors as defined by local, regional, state, national and/or international governing entities.

Once an applicable retention period has elapsed for a given type or series of information, and all holds/moratoriums have been released, the information is typically destroyed using an approved and effective destruction method, which renders the information completely and irreversibly unusable via any means. Information with historical value beyond its "usable value" may be accessioned to the custody of an archive organization for permanent or extended long-term preservation.
-- Wikipedia
Legal Definition
The number in years that records must be kept as stated by law.