CGST, SGST and IGST — The Difference on an Invoice

The rule, in one line

A sale where the seller and the place of supply are in the same state is taxed as CGST plus SGST. A sale where they are in different states is taxed as IGST, at the same combined rate. Nothing else about the invoice differs — the items, the taxable amount and the grand total are identical either way.

This is why the place of supply field matters so much. It is the field that decides which of the two it is.

CGST and SGST: a sale within one state

For an intra-state sale the tax rate is halved. A line taxed at 18% carries 9% CGST and 9% SGST, and the invoice shows both rows. The two halves are always equal, because they are two halves of one rate.

The example below is a Gujarat seller billing a Gujarat buyer. Look at the tax rows at the foot of the sheet: CGST and SGST, each exactly half.

IGST: a sale across states

For an inter-state sale the whole rate is charged as IGST, in a single row. The same two lines, taxed at 18%, now produce one IGST figure — and that figure is the sum of the two halves above, to the paise.

Below is the same sale billed to a Maharashtra buyer. Only the place of supply and the buyer's details have changed, and the tax rows have collapsed from two into one.

Reading the two side by side

Put the two sheets above next to each other and the difference is visible in exactly two places: the place of supply box in the bill-to block, and the tax rows in the totals. The taxable amount is the same. The grand total is the same. If the grand total ever differs between an intra-state and an inter-state version of the same sale, something else has changed — a rate, a quantity or a discount — because the tax treatment alone cannot move it.

Where the place of supply appears on the sheet

On a tax invoice the place of supply is normally shown as its own box in the bill-to block, beside the buyer's details, because it is a property of the supply rather than of either party. Putting it there means a reader can see how the tax was treated without having to work backwards from the tax rows.

It is worth filling in even when it looks redundant. Leaving it blank does not make a sale intra-state — it leaves the treatment to be inferred from the two states, which is the same calculation but written nowhere on the page. An invoice whose tax split has to be reconstructed is one that gets queried later.

Three ways the two get mixed up

Most of the confusion in practice comes down to three things, and all three are visible on the sheet rather than hidden in the arithmetic.

• Deciding the treatment from the buyer's billing address instead of the place of supply. The two are usually the same and are not always.
• Reading IGST as a higher rate. It is the same combined rate, charged as one line rather than two.
• Showing CGST and SGST as unequal halves. They are two halves of one rate, so they are always equal — an invoice where they differ has a rounding problem somewhere upstream.

Why the split matters to a business

The split is not cosmetic. CGST and SGST are collected by different governments, so a single IGST figure and a CGST-plus-SGST pair are not interchangeable in a business's records — they are reported differently and they are claimed differently.

That is also why a buyer who has been charged the wrong one cannot simply be asked to ignore it. Which treatment applies to a given sale, and how to correct a document that used the wrong one, is a question for a CA.

Common questions

Is the total the same for CGST/SGST and IGST?

Yes, provided the rate is the same. The tax is identical in total; it is only divided differently — two halves or one whole.

What decides whether a sale is intra-state or inter-state?

The seller's state against the place of supply. Where the two match the sale is intra-state; where they differ it is inter-state.

Can an invoice show CGST, SGST and IGST together?

Not on an ordinary sale. A single invoice is one or the other, because a single supply has one place of supply. An invoice mixing both is normally a sign that the place of supply was set to different values on different lines.

Is IGST always a higher rate than CGST plus SGST?

No. IGST is the same combined rate, charged as one line instead of two.