If there is default in payment of tax and filing of returns, interest is payable on gross tax payable or net tax payable

Gross tax payable, if there is default in payment of tax and filing of returns, input tax credit will become ineligible as per Section 16(2) of the CGST Act. Therefore, the taxable person will not be allowed claim set-off of input tax credit for calculation of interest.

(ICAI FAQ PUBLICATIONS 06-09-2017 TAX PAYMENTS, INTEREST, PENALTY AND OTHER AMOUNTS: FAQ NO. 35)