IGST errornously entered in GSTR 3B

I have erronously entered IGST figures in 3 months of FY 17-18 as IGST but never adjusted against any liability and in october , 18 i realised my mistake and reversed it. in sept, 18. Can anyone tell me if i am liable for interest . Which section to quote while replying to officer for demand of taxes and interest? any case law? its urgent please.