The CAA has recently been in receipt of licence renewal and variation applications where the original licence returned to the CAA was not signed by the licence holder.
By not signing the licence, the privileges of the licence cannot be exercised. Any maintenance and associated Certificate to Release to Service issued using an unsigned licence is invalid and therefore invalidates the C of A / ARC of the aircraft.
Licence holders must sign the licence immediately on receipt to render the licence valid. Maintenance Organisations must ensure their certifying staff have signed their licence prior to issuance of an Organisation Authorisation.