QUOTE
As for alltitude reporting, if the passing level is not given in the initial contact then you DO NOT HAVE A RADAR SERVICE. The transponder is NOT verified and in a court of law you wouldn't stand a chance.
UNQUOTE
Just to clarify this: Mode C is only considered as verified when it has been cross checked on the radar display with a level report from the aircraft. This is usually the first radar unit on departure, but may also be an en route sector if you are joining airways from an airfield outside. Once this has been done, the Mode C is considered verified for the rest of the trip unless there are suspicions that it may be incorrect.
Thus, there is no need to give passing level on EVERY new frequency because they are not using that information to reverify your mode C.
However, a 'level passing' report can sometimes be a good trigger for further climb/descent clearance.