A good attorneyclient retainer agreement details how the retainer fee will be used. Retainer fees are an important part of any legal case.Learn how to pay them in a way that best suits your needs. Subject to the terms of this retainer agreement, in the event any bill from this firm remains unpaid beyond a 30-day period or, if in the judgment of this firm. You should have a retainer agreement or an engagement letter with your client, outlining the scope of the services you are providing. This client Retainer Agreement is for ongoing service agreements between a client and consultant or contractor. This document outlines a retainer contract between Camp John Hay Development Corporation and the law firm Formoso and Associates. The way I've done it in the past for nonretainer work is to have it essentially written as a zero hours master services contract with firm SLAs in it. Non-engagement letter. This agreement should cover elements like the services you'll provide, how long the working relationship will last, fees, pricing, confidentiality, and more.