Addition of unaccounted supplies in the Returns - Goods and Services Tax - GST

My client s POB was visited by DGGI staff. After the search is over they asked to pay 5 lakh towards unaccounted sales/supplies verbally and accordingly DRC-03 was filed. Though this is all without authority of law the dealer do not want to contest any litigation neither apply for refund. We have also received closer report from the DGGI office on the basis of voluntary payments. How to show this turnover in GST returns? As tax is already paid through DRC-03 how to offset the additional liability? How to show all this in GSTR-9 and 9C ? Can we file returns with regular turnover as per books without adding this turnover as this is fictitious turnover? We have not incorporated this turnover in books of accounts.