The GST everyone knows is the straightforward add-or-remove calculation: take a base price, apply 5%, 12%, 18% or 28%, and you have the tax.
About this calculator
The GST everyone knows is the straightforward add-or-remove calculation: take a base price, apply 5%, 12%, 18% or 28%, and you have the tax. What most calculators skip is the three situations that cause the real confusion at invoice time. One, composite scheme: small businesses under the threshold pay a flat 1% (traders and manufacturers), 5% (restaurants) or 6% (services) on turnover instead of the regular rate, and they cannot charge GST to customers or claim input tax credit. Two, reverse charge: certain categories of supply shift the tax liability from the supplier to the recipient, who must pay the GST directly to the government and then claim it back as input credit if eligible. Three, the CGST-SGST split versus IGST: intra-state transactions split the tax equally between the central and state governments, while inter-state transactions levy a single IGST that the centre collects.
This calculator handles all three modes in one place. Switch the scheme dropdown between regular and composite to see how a 18 lakh annual turnover is taxed under each. Flip the inter-state toggle to see the split change from CGST plus SGST to a single IGST row. Choose reverse-charge when you are the recipient of specified services like legal advice from an advocate or GTA transport, where the supplier does not charge GST on the invoice but you still owe it.
For basic invoicing, see [[gst]] which is faster for the add-or-remove case. For the import of goods, customs duty sits on top of IGST -- that is a separate calculator. Composite scheme traders cannot charge GST to customers, so do not use the add-mode output as an invoice number under that scheme.
Common uses
- Small trader deciding between regular 18% GST with input credit and 1% composite scheme
- Restaurant under the 5% composite scheme computing monthly tax on turnover
- Inter-state service exporter splitting IGST from intra-state CGST+SGST invoices
- Recipient of advocate or GTA services computing reverse-charge liability
- Pulling the pre-GST base price out of a gross invoice with 18% tax included
Frequently asked questions
What is the composite scheme in GST?
A simplified tax scheme for small businesses: pay a flat rate on turnover (1% traders and manufacturers, 5% restaurants, 6% services) instead of the regular GST rates. The composite dealer cannot charge GST on invoices and cannot claim input tax credit, in exchange for lighter compliance.
Who pays GST under reverse charge?
The recipient of the supply pays, not the supplier. Notified services like advocate fees, sponsorship services, GTA transport, and purchases from unregistered suppliers trigger reverse charge under Section 9(3) and 9(4). The recipient self-invoices, pays the tax, and claims it back as input credit if their output is taxable.
Is it IGST or CGST plus SGST for my invoice?
If supplier and recipient are in different states or union territories, it is IGST. If they are in the same state, it is CGST plus SGST, each being half of the applicable rate. Place-of-supply rules can get tricky for services -- the location of the service recipient usually determines the state.
Can I switch between regular and composite scheme?
Yes, at the start of a financial year with Form GST CMP-02 to opt in or CMP-04 to opt out. Once opted out during the year you cannot opt back in. The composite threshold is 1.5 crore turnover for goods (most states) and 50 lakh for services across all states.
How do I reverse-calculate GST from a gross price?
Divide the gross by (1 + rate). For 18% GST on a gross of 11,800, the base is 11800 / 1.18 = 10,000 and the GST is 1,800. Use the Remove GST mode in this calculator to do this automatically for any rate.