This discussion clarifies how to handle credit and debit notes from vendors that appear in GSTR 2A. You should book these memos in your accounts, adjusting your input tax credit accordingly. For subsequent months, reduce your current month's ITC by the note's value and report the net figure in the 'all other ITC' section of your GSTR 3B.
22 December 2020
you should have to book purchase credit memos / purchase invoice in your books .........and increase/reduce your input tax credit for the above.
22 December 2020
Reduce the same in the subsequent month ITC and show net figure in all other ITC tab of GSTR 3B. Eg : CN -10 and ITC for current month -100 then show 90 in all other ITC tab