I have a GST registered client filing GSTR-1 monthly. While filing GSTR -1 for the Month of October -2021, Supply outward made to a GST registered customer wrongly shown as B2C supply outwards. Today customer have approached client regarding the issues as they have got notice from the GST in respect of the unaccounted purchases. How can my client rectify the said mistake. Whether it was possible at the time of filing GSTR-1 for the month of September-2022. Please address the issue.