What is the difference between CGST, SGST and IGST, and when does each apply?

CGST (Central GST) and SGST (State GST) are charged together on an intra-state supply, that is, when the supplier's location and the place of supply are in the same state. The GST rate is split equally between them: for an 18% supply, 9% is CGST and 9% is SGST. In a Union Territory without a legislature, UTGST replaces SGST.

IGST (Integrated GST) is charged on an inter-state supply, and also on imports and exports, at the full GST rate. For an 18% supply, the whole 18% is IGST. The place of supply rules in the IGST Act decide whether a supply is intra-state or inter-state, so for goods it is usually where the goods are delivered, not where the invoice is raised.

On the invoice, show CGST and SGST as two lines for intra-state sales, or a single IGST line for inter-state sales. If you are unsure how the rules apply to a particular transaction, confirm with your CA or tax advisor.