GSTR 1 Mistek ?

vikram kerekar (1244 Points)

08 August 2018  
i have miestkly file 3-B and GSTR -1 for the month of Dec and Jan wrongly shwon in two parties sale bill and today i have final all accounts till 31.3.2018 that time i have found this mistake so how can i rectify this mistek pls all experts give solution.