GST R 1 And 3 B difference

File Correct GSTR-9 and if liability is short paid into GSTR-3, then pay it through Form DRC-03.

If excess output tax has been reported in GSTR 3B , & your GSTR 1 is filed correct then Nothing is to be in GSTr 9 as the Outward supply & tax in table 4 of GSTR 9 is autopopulated from GSTR 1.

If your 3B is filed correct but In GSTr 1 you have made the mistake & the same has not been rectified till 31/3/2019 then Amend the autopopulated figures in table 4 & table 9 (output tax) of GSTR 9