Side letter

A side letter or side agreement is a collective bargaining agreement that is not part of the underlying or primary collective bargaining agreement (CBA), and which the parties to the contract utilize to reach agreement on issues the CBA does not cover, to clarify issues in the CBA, or to modify the CBA (permanently or temporarily). One may distinguish side letters from "side settlements" or "settlement agreements", which settle a dispute arising from the underlying CBA. In rare cases, bargaining parties may use a side letter to adjust the focus of the contract if the parties are not yet ready or willing to adapt the contract formally.