We have wrongly taken input credit month of Dec'2017, after all clarifications this month we have decided to reversal the input so how much rate of interest and which date i have to take to calculate the interest i.e Supplier invoice date or GST filled date.
11 September 2018
If You are wrongly availed on Dec-17. The return date is 20/01/2018 then You will calculate from 21/01/2018 to Till date or next return which you are reversed...
Also note if any liability on Dec-17 then pay with Interest...