On a perusal of the provisions relating to mismatch of input tax credit, it is noticed that the tax payable on account of mismatch of input tax credit is added to the output tax liability of the recipient. Why is the recipient penalised for such mismatch?

As per section 155 of the CGST Act, if any person claims input tax credit, then the burden of proving such claim lies on him. Therefore, if the supplier does not declare the supplies or declares output tax lower than the amount claimed as credit, the recipient is burdened with the differential tax liability.

(ICAI FAQ PUBLICATIONS 06-09-2017 RETURNS : FAQ NO.37)