sac code mentioning

Notification No. 12/2017 – Central Tax

Turn Over  1. Upto rupees one crore fifty lakhs............. Nil

2. more than rupees one crore fifty lakhs and upto rupees five crores ...........2

3. more than rupees five crores ,,,,,,,,,,,,,,,,,,,,,,  4 

Yes, for sac code just 4 digits are required to be mentioned for all, (except for import/export, where 6 digits would apply)

There is no specific notification for SAC code, and general interpretation is that the same notification holds good for SAC code also. But as all services have comman first two digits '99'; so its better to specify 4 digits to distinguish it as different group.