Place of supply: why an invoice shows IGST instead of CGST

What place of supply means

Place of supply is the state where a sale is treated as happening. For ordinary goods and services billed to a business, that is your customer's state — which is why the state you save on a customer matters as much as your own.

It is not a setting you switch. It follows from your GSTIN's state and the customer's state, and Dukaaan works it out for every line on every invoice.

Same state, or another state

Billing a customer in your own state is an intra-state supply: the tax splits into CGST and SGST, half each. Billing a customer in a different state is an inter-state supply: the whole amount is IGST instead.

The total tax is the same either way. Only the split changes, and only the split is what your return cares about.

You never pick CGST, SGST or IGST by hand. If the split looks wrong, the state on the customer or on your business profile is what to check — not the invoice.

When the split looks wrong

Almost always this is a missing or wrong state on one of the two parties, not a tax bug. Check them in this order:

1. Open the customer and check the state on their address. A customer saved without a state cannot be classified, and an invoice to them will not split the way you expect.
2. Check your own state in Settings → Business & branding. It comes from your GSTIN and is the other half of the comparison.
3. Correct whichever is wrong, then raise a fresh invoice. A finalized invoice keeps the split it was issued with — see Fix a mistake on an invoice you already finalized.