Circumstances The crew of VH-EWD had flight planned for a regular public transport flight from Canberra to Coolangatta using the route designator C4CBCGXX where XX is the modifier for that particular route. The Melbourne computer aided flight strip printing system interpreted the XX modifier as a track via Bindook and Sydney. The systems used by the airline and Canberra Air Traffic Services (ATS) interpreted XX as a track via Yass and Mudgee. The Civil Aviation Authority (CAA), while retaining the XX modifier, had recently changed the applicable route from Bindook/Sydney to Yass/Mudgee. The airline and Canberra ATS had effected the appropriate software changes for the route modifier whereas Melbourne ATS had not. EWD departed Canberra at 0850 EST and tracked via the Yass/Mudgee route as expected by Canberra Air Traffic Control (ATC). As the vertical limit of Canberra ATC is 10,000 ft, co-ordination procedures between Canberra and Melbourne Sector require the notification of an impending departure to be given to Melbourne prior to the aircraft becoming airborne. On this occasion co-ordination was not carried out until after EWD had departed. Additionally, when Canberra Approach informed Melbourne Sector of EWD's departure, the controller incorrectly referred to the aircraft as EWG. On receiving the departure advice the Melbourne controller actioned his EWD flight strip and changed the callsign to EWG. The track details on his strip indicated a track via Bindook and Sydney. As there was no other traffic in that portion of airspace, he elected to wait until he had confirmed the callsign with Canberra and observed the aircraft on radar before taking any additional amendment action. At 0853 Melbourne Sector contacted Canberra Approach to confirm the callsign of the aircraft on the Yass track as their radar was indicating EWD. Further co-ordination took place between Melbourne and Canberra, which confirmed that the Coolangatta bound aircraft was tracking via Yass and Mudgee. The Melbourne controller subsequently amended all details held in the Area Approach Control Centre for the flight and EWD proceeded without incident. There was no breakdown in separation and the transfer of responsibility from Canberra to Melbourne was performed in accordance with the prescribed procedures. CONCLUSION Significant Factors The following factors were considered relevant to the development of the incident. 1. Melbourne ATS had not made the necessary software changes for the route, thus the route modifier being used by Melbourne ATS was incorrect. 2. Canberra Approach Control did not co-ordinate the impending movement of VH-EWD with Melbourne Sector prior to its departure. 3. Canberra Approach Control subsequently used an incorrect callsign when co-ordinating VH-EWD's departure. SAFETY ACTION In response to safety deficiencies identified during this investigation the CAA amended their procedures for the allocation of route designator modifiers. The CAA airspace and air-route structure reviews are changing the parameters of design in respect to these problems and intend that all the new air routes will require new route modifiers for flight planning purposes.