This discussion addresses how to settle outstanding GST for the financial year 2019-20 after the September GSTR 3B has been filed. It explains that balance GST can be paid via the cash ledger by filing Form DRC-03. While missing B2C sales from 2019-20 can be added to the October GSTR 3B, the advice leans towards using DRC-03 for direct payment and correcting details in the GSTR9 annual return for 2019-20.
But my view to instead of showing in October month 3B & making reconciliation statement for 2020-21 , it's better pay in cash ledger & file DRC 03 , Moreover can correct in table 4 of GSTR9 for 2019-20