These firms, most of them just shell-companies, submitted bogus bills for the amount totalling Rs 400 crore, said Secretary of Commercial Tax Department R S Vishwakarma.
Tax-payer Identification Number (TIN) of these firms was subsequently cancelled, he told PTI.
Software wing of the department found recently that these firms had issued bills without any transfer of goods.
This allowed the purchasing dealers to claim the input tax credit, which led to evasion of Rs 20 crore in tax.