CGST, SGST, IGST explained: how GST splits on your invoices

On a GST invoice, the same total tax shows up either as CGST + SGST (for a sale within your state) or as IGST (for a sale to another state). The total GST rate is the same — what changes is whether it's split between the centre and your state, or charged as a single inter-state tax. That single rule explains almost every GST invoice you'll ever raise.

The three taxes in one minute

• CGST — Central Goods and Services Tax, collected by the central government.
• SGST — State Goods and Services Tax, collected by the state government (called UTGST in union territories).
• IGST — Integrated Goods and Services Tax, collected by the centre on inter-state supplies and then shared with the destination state.

GST is a destination-based tax: revenue ultimately belongs to the state where the goods or services are consumed.

The deciding factor: place of supply

Whether you charge CGST+SGST or IGST depends on whether the supply is intra-state (within one state) or inter-state (across states).

• Intra-state supply (supplier and place of supply in the same state) → CGST + SGST.
• Inter-state supply (supplier and place of supply in different states) → IGST.

The total rate doesn't change. An 18% item is 18% either way — it's just collected differently.

How the split works

For an intra-state sale, the GST rate is divided equally between CGST and SGST.

If the GST rate is 18%:

• CGST = 9%
• SGST = 9%

For an inter-state sale at the same 18%:

• IGST = 18% (single line)

Worked example 1: intra-state (within the same state)

You're in Maharashtra and sell to a customer in Maharashtra. Taxable value: ₹10,000, GST rate 18%.

• CGST 9% = ₹900
• SGST 9% = ₹900
• Total tax = ₹1,800, invoice total ₹11,800.

Your invoice shows two tax lines: CGST and SGST.

Worked example 2: inter-state (different states)

You're in Maharashtra and sell to a customer in Karnataka. Same ₹10,000 at 18%.

• IGST 18% = ₹1,800
• Total tax = ₹1,800, invoice total ₹11,800.

Your invoice shows one tax line: IGST. Note the total tax is identical — only the breakup differs.

Why it matters on your invoice

Getting the split right is a compliance requirement, not a formatting choice:

• The wrong tax type (charging IGST where CGST+SGST applies, or vice versa) creates mismatches in your returns and can affect your buyer's input tax credit.
• The place of supply rules (especially for services) can be nuanced, so for unusual cases it's worth checking the specific rule.

How software handles this for you

Good billing tools determine the supply type automatically from the supplier's state and the customer's place of supply, then apply CGST+SGST or IGST without you doing the maths. In Invoicify, you simply set the GST rate on each line and pick the client; the correct split is generated on the invoice.

Quick recap

• Same state → CGST + SGST (rate split in half).
• Different states → IGST (single line, full rate).
• The total GST is the same either way — only the breakup changes.

Once "place of supply decides the split" clicks, GST invoicing stops feeling mysterious. Everything else is just applying the right rate to the right line.