The SLA for the service sets out the aims and objectives for the service and is agreed with commissioners (NSD) on a 1-3 year basis. It describes how the service is set up and expected levels of activity. The SLA also describes the NHS systems and medico-legal framework that the service operates in. It also establishes the reporting and financial arrangements agreed by the service.
Many SLAs may have a 'DRAFT' watermark. This is because the final (signed) SLA is typically a paper document. It is unusual for there to be major changes.