IFR Departure Message
CAP 413 Ch6, para1.1.2 refers.
Pilots of all aircraft flying Instrument Departures are to include the following information on first contact with approach control / departure radar:
a) Callsign
b) SID Designator where appropriate
c) Current or passing Alt/FL PLUS
d) Cleared Alt / FL
CAP 413 is, of course, specific to UK.