Penalty calculation under IGST Act: ten percent of combined tax, computed by summing CGST and SGST penalty amounts. The fourth proviso to the IGST Act mandates that the penalty for integrated tax is the sum total of the monetary penalties leviable under the CGST and SGST Acts; therefore IGST penalty is computed by adding the penalty amounts determined under each Act (not by adding penalty rates), resulting, for example, in a ten per cent penalty on the combined tax amount where CGST and SGST each attract ten per cent penalties.