Date of Increment after M.A. Scale

My Basic pay was 5900 in Sep 1998 when I passed M.A. and the Basic was fitted to 6000 (lowest in the 6000-12000 band). Now what should be the date of increment? When I was enjoying Hons Scale, my normal increment date was 1st January. Please provide me relevant G.O. or others because, probably I have to rectify my Service Book depending on the answer.