After the aircraft had commenced taxiing for takeoff the crew were advised that the aircraft had been loaded out of trim. The aircraft was returned to the gate while adjustments to the load were made. To enable the aircraft to be loaded within the weight and balance limits the load control officer planned for a nil uplift in hold 4. A load instruction report was prepared indicating a nil uplift for hold 4, and was handed to the ramp leading hand. After loading was completed the ramp leading hand presented a ramp clearance report to the load control officer. It was noted that twenty bags had been loaded into hold 4. Accordingly the load control officer recalculated the weight and balance, found that the aircraft was out of trim, and recalled the aircraft. The operators procedures require the ramp leading hand to advise the load control officer of any changes before the changes are made. These procedures were not followed and the company has initiated measures to improve discipline in the loading area. The aircraft was operating under a new centralised load control system that allows the aircraft to be released from the gate prior to obtaining a final load clearance. The final loadsheet data is transmitted by radio to the aircraft and a hard copy is printed on the flight deck by the crew. System safety is assured as final loadsheet data cannot be transmitted by the load control officer until after the passenger and ramp clearances have been received and any loading adjustments made in the system. Also, the system will not produce a loadsheet if the weight or trim is outside limits, and the crew will not be able to configure the aircraft for takeoff without first having received the loadsheet data.