filing of GSTR 9

No by GSTr 9 you cannot claim by any reversing of OutputTax liability.

That is to be corrected & would have reversed in GSTr 3B by 31/3/2019.

Change the autopopulated output tax liability in table 4 & change the same accordingly in table 9, that's all ...your GSTR 9 will get tally with your books of account

but 31st march 19 has already been passed

The DUE DATE for furnishing of Annual Return in the FORM GSTR-9 / FORM GSTR-9A and Reconciliation Statement and Audit Report in FORM GSTR-9C for the financial year 2017-18 has been extended from 31st August, 2019 to 30th NOVEMBER, 2019.

REMOVAL OF DIFFICULTY ORDER No. 07/2019-CT dated 26.08.2019, issued by the CBIC Department.

Hence, the latest Due Date to file ANNUAL RETURN ( GSTR-9 and GSTR-9A ) and Reconciliation Statement and Audit Report ( GSTR-9C ) is 30.11.2019.