Final invoice amount
₹11,800.00
GST on an invoice is worked out on the taxable value — the amount left after any discount, before tax is added. The formula is straightforward:
Whether that GST amount is charged as CGST + SGST or as IGST depends on where the buyer and seller are located — see below. This is general information, not tax advice; for your specific filing, confirm the applicable rate and treatment with a CA.
India's GST splits into three components depending on whether a sale happens within a state or across state lines:
Central GST — charged on intra-state sales, alongside SGST. Goes to the central government.
State GST — charged on intra-state sales, alongside CGST. Goes to the state government.
Integrated GST — charged instead of CGST+SGST on inter-state sales, at the full rate.
For an intra-state invoice, CGST and SGST are each exactly half the applicable GST rate — 9% + 9% for an 18% rate, for example. For an inter-state invoice, IGST is charged at the full rate instead.
To find a GST-inclusive amount from a taxable value, multiply by (1 + GST rate ÷ 100). To go the other way — pulling the taxable value and GST back out of a total you already received — divide instead:
Adding GST (same state)
₹10,000 taxable value at 18% GST →
CGST ₹900 + SGST ₹900 = ₹1,800 GST
Final invoice amount: ₹11,800
Removing GST
₹11,800 including 18% GST →
Taxable value ₹10,000 + GST ₹1,800
GST portion: ₹1,800
Beyond the GST math, a valid GST invoice generally needs:
Working out the GST is only half the job — you still need to put it on a properly formatted invoice. See our GST invoice format guide, or skip the manual work with the free invoice generator, which calculates the CGST/SGST/IGST split automatically as you fill in an invoice.
GST amount = Taxable value × GST rate ÷ 100. The final invoice amount is the taxable value plus this GST amount. If the sale is within the same state, the GST amount is split equally into CGST and SGST; if it crosses state lines, the full amount is charged as IGST.
CGST (Central GST) and SGST (State GST) apply together on an intra-state sale — each is half the applicable GST rate, and one goes to the central government, the other to the state government. IGST (Integrated GST) applies on an inter-state sale instead, at the full rate, and is later apportioned between the states involved.
Multiply the taxable value by (1 + GST rate ÷ 100). For example, ₹10,000 at 18% GST gives a GST-inclusive amount of ₹10,000 × 1.18 = ₹11,800.
Divide the GST-inclusive total by (1 + GST rate ÷ 100). For example, ₹11,800 at 18% GST gives a taxable value of ₹11,800 ÷ 1.18 = ₹10,000, meaning ₹1,800 was GST.
Common GST rates include 0%, 5%, 12%, 18% and 28%, depending on the goods or service. Some professional and consulting services may be taxed at 18%, but the applicable rate depends on the specific service and current GST classification. Always confirm the exact rate before issuing an invoice.
Yes. Only a business registered under GST (with a valid GSTIN) can legally charge GST on an invoice and claim input tax credit. This calculator is for working out the numbers — it does not check your registration status.
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