The CRS has to be issued always by certifying staff of the Part-145 organisation. must have procedures to verify that all the maintenance ordered to that organisation has been released to service by the approved Part-145 organisation.
The Release To Service (RTS) authorizes Military Operated (In-Service) Defence Air Environment (DAE) Operating Category flying on behalf of the responsible Senior Duty Holder. Any failure by operators or the Aviation Duty Holder to observe RTS limitations may result in unacceptable hazards to aircrew or other parties.
A certificate of release to service is necessary before flight, at the completion of any defect rectification, whilst the aircraft operates a flight between scheduled maintenance checks.
50(d), a certificate of release to service is issued by appropriately authorised staff at the completion of any maintenance on a component, whilst the component is off the aircraft.
A Certificate of Release to Service (CRS) is a declaration made by appropriately authorised personnel once it has been verified that task being signed for has been properly carried out.