A retainer in professional services is an upfront fee paid by a client to secure the services of a consultant, attorney, or other professional for a specific period. This financial arrangement is often used for projects with an uncertain scope or duration, serving as a kind of insurance that the professional will remain available to the client. Retainers are commonly used in legal practices but can also be found in consulting, advertising, and freelancing environments. They are sometimes a flat fee but can also be a percentage of the estimated cost of a project. Retainer agreements usually outline the specific terms under which the retainer will be applied, such as the hourly rate for services and how many hours the retainer covers. Retainers offer professionals a more predictable income stream and help to cover basic expenses during slow periods. For clients, they offer the assurance of having expert help readily available when needed, but they must also exercise due diligence to ensure that services are rendered in a manner commensurate with the retainer fee.