The Finance Ministry has permitted businesses to rectify mistakes in their monthly returns - GSTR-3B - and adjust tax liability, a move that will help them file correct returns without fear of penalty.CBEC said while making adjustments in the Output Tax Liability or Input Tax Credit, there can be no negative entries in GSTR – 3B. The initial GSTR 3B summarized return, has to be filed by businesses by 20th day of every month for the previous month showing details of taxes paid.