Wrong head pay

There is no issue if you have mistakenly paid the amount in CGST & SGST instead of IGST.

Calculate the amount of IGST that was payable and pay it and file your return.

The excess amount which you have paid in CGST & SGST. It will show in GST cash ledger balance. You can use that balance amount in your next return payment.

1) Now, deposit the tax under the correct head. 

2) Interest liability shall not be there.

3) The tax which have been deposited wrongly while filing return can be applied to the department for refund.

In case of any further queries, kindly mail me at casoravgupta @ gmail.com

Thanks & Regards
CA. Sorav Gupta
(Practicing Chartered Accountant)