In the FY 2020 - 21, we were under QRMP scheme. While filing the GSTR1 return for Q4 in March 21, we ommited the sales for the month of Jan and Feb ( B 2 C sales ) and entered only the turnover for that month in the relevant table. Later, in April 21, we realized the mistake and filed an amendment for B2C sales for March 21 in GSTR 1 of April 21. But, ironically, now we find that, a portion of the B2B sales also has been included in the amendment made in B2C table. When we went for another amendment in the subsequent GSTR 1 return, the portal is not permitting us to do so, stating that, already an amendment has been made. Now, how shall we rectify the error. Pls. advice.