GSTR3B filed with tax paid instead of nil data

GSTR3B for the month of September 2020 was filed with tax liability, but actually it was having NIL data but due to data entry error supply was mentioned and tax was paid and in actually gst was not payable. Now the business is going to close it's business and no further returns are required to file. So under the circumstances what is the remedy to get back that wrong tax paid.