After detail search on internet, I found an amendment -
As per the GST act amendment 31 of 2018 as on 29 aug 2018, section 49 of the principal act was amended as -
In section 49 of the principal Act,–
(b) in sub-section (5),–
(i) in clause (c), the following proviso shall be inserted, namely:–
“Provided that the input tax credit on account of State tax shall be utilised towards payment of integrated tax only where the balance of the input tax credit on account of central tax is not available for payment of integrated tax;”;
(ii) in clause (d), the following proviso shall be inserted, namely:–
“Provided that the input tax credit on account of Union territory tax shall be utilised towards payment of integrated tax only where the balance of the input tax credit on account of central tax is not available for payment of integrated tax;”.
Therefore, one cannot utilise them equally. You need to exhaust chat first and then only sgst input could be used for IGST.