Add or remove GST from any amount at India's standard slab rates.
GST is added to a base price at the applicable slab, so a price of 100 at 18 per cent becomes 118. Removing it works backwards from the inclusive figure, and this is where most errors happen: you do not subtract 18 per cent from 118. You divide by 1.18, giving roughly 100, because the 18 per cent was calculated on the base, not on the total. Subtracting 18 per cent from 118 gives 96.76, which is wrong by a meaningful margin and is easily the most common GST mistake in practice.
Two structural points are worth knowing. GST splits into CGST and SGST for a sale within a state (half each) or a single IGST for an inter-state sale — the total is identical, only the allocation between centre and state differs. And GST is a value-added tax, so a registered business claims input tax credit on GST already paid on purchases and remits only the difference. The tax is designed to fall on the final consumer, which is why a registered business generally treats GST as a flow-through rather than a cost, and why unregistered buyers bear it in full.
Divide by one plus the rate as a decimal. At 18 per cent, divide the inclusive amount by 1.18. Subtracting 18 per cent from the inclusive figure gives a different and incorrect answer, because the tax was calculated on the base price.
For a sale within a state, GST splits equally into CGST (centre) and SGST (state). For an inter-state sale a single IGST applies instead. The total rate is the same either way; only the allocation differs.
It lets a registered business offset the GST it paid on purchases against the GST it collects on sales, remitting only the difference. This is what makes GST a tax on value added rather than a tax charged again at every stage.
No. Only registered businesses may collect GST, and registration is mandatory above the turnover threshold. Charging GST without registration is not permitted, and unregistered buyers cannot claim input credit on what they pay.