A retainer agreement is a contract between a client and a professional who requires an upfront payment applied to future work. No other agreement, statement or promise made on or before the Effective Date of this Agreement will be binding on the parties.This retainer agreement outlines the terms of a pro bono legal assistance relationship between an attorney and a client agency. Creating a retainer agreement can be an essential part of protecting both parties in any professional relationship. A fee retainer agreement a type is a contract where a client or customer pays in advance for professional services and work product to be specified later. This client Retainer Agreement is for ongoing service agreements between a client and consultant or contractor.