The short version
For most domestic supplies, the distinction is straightforward:
- Intra-state supply: GST is split between CGST and SGST (or UTGST, where applicable).
- Inter-state supply: GST is charged as IGST.
The important detail is that this is determined by the GST place-of-supply rules, not simply by looking at the customer's mailing address.
Intra-state supplies: CGST and SGST
When the location of the supplier and the place of supply are in the same state, the transaction is generally treated as an intra-state supply.
The GST rate is then divided equally between Central GST and State GST. If the applicable GST rate is 18%, the invoice would normally show:
- 9% CGST
- 9% SGST
In a Union Territory where UTGST applies, UTGST takes the place of SGST.
Inter-state supplies: IGST
When the location of the supplier and the place of supply are in different states or Union Territories, the transaction is generally an inter-state supply and IGST applies.
At an 18% GST rate, the invoice would show 18% IGST rather than separate CGST and SGST amounts.
A simple example
Suppose the taxable value of a service is ₹10,000 and the applicable GST rate is 18%.
For an intra-state supply:
- Taxable value: ₹10,000
- CGST at 9%: ₹900
- SGST at 9%: ₹900
- Total: ₹11,800
For an inter-state supply:
- Taxable value: ₹10,000
- IGST at 18%: ₹1,800
- Total: ₹11,800
The total tax is the same in this example. What changes is how that tax is reported on the invoice.
Why place of supply matters
"Same state" is useful shorthand, but GST law uses specific rules to determine the place of supply. Those rules can vary depending on whether you are supplying goods or services and on the circumstances of the transaction.
For an ordinary invoice, make sure the supplier location and place of supply are correct before relying on the CGST/SGST or IGST split.