Question

why igst introduced instead we can levy cgst and sgst​

Answer 1

Ideally, for an intra-state supply, the tax collected should be CGST/SGST instead of IGST. To rectify the situation, the person concerned will have to pay CGST/SGST and get the refund of the amount paid as IGST.

I hope it will help you☺

Fóllòw Më ❤