A service level agreement (SLA) is a written contract between a service provider and a client that specifies the services requested and the degree of service expected. Vendors, services, and industries all have different agreements.

SLAs are meant to keep both parties accountable. If there is a problem with the service, the SLA serves as necessary documentation, describing all of the measurements, obligations, and expectations that were agreed upon from the start. Because both parties have access to the SLA, neither can later claim that they were unaware of the expectations or agreed-upon standards.