In case of first year i.e. year of registration with sales-tax department, Six Monthly in within 21days of end of the half year. In Form 231 for MVAT Return and in Form III-B for CST return. In case of Subsequent year: File monthly return within 21 days of end of the month, if tax liability during previous financial year exceeds Rs.10,00,000/- or refund during previous financial year is Rs. One Crore. File quarterly return within 21 days of end of the quarter, if tax liability during the previous year exceeds Rs. One lakh but did not exceed Rs.Ten Lakh, or Refund during the previous year exceeds Rs.10 Lakhs but did not exceed Rs.1 crore File six monthly return if during the previous year tax liability did not exceed Rs.One Lakh or Refund during the previous year did not exceed Rs.Ten Lakh