What is a retainer agreement? A retainer agreement is a contract between a company and a service provider that defines the details of a retainer agreement, for example. B the duration of the period of re-termination, the payments made and the details of the termination. […] instead of making them sign the same engagement letter as the client; This maintains a lawyer`s privilege of the fee agreement with […] The extension of the period for the execution of this Agreement may be granted by the Company, agreed in writing and signed by both Parties during the term of this Agreement. . . .