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GST Reverse Calculator

Already have a price that includes GST? Enter it here and the calculator works backwards to the taxable value and the tax you must report in GSTR-1. Not sure whether a price includes GST? See GST inclusive vs exclusive meaning.

Useful for MRP-based retail, cash bills written as a round figure, and reconciling payment gateway settlements where the customer paid one inclusive amount.

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Common slabs are 0, 5 and 18, plus a 40% special rate for luxury and sin goods. Any custom rate works too.

Reverse GST breakdown

Taxable value (excl. GST)Total GST
Taxable value (excl. GST)
₹10,000.00
Total GST
₹1,800.00
CGST @ 9%
₹900.00
SGST @ 9%
₹900.00
Invoice total (incl. GST)
₹11,800.00
Taxable value = inclusive amount ÷ (1 + GST rate ÷ 100).

Of the ₹11,800.00 total, ₹10,000.00 is the actual taxable value and ₹1,800.00 is GST: the split you need for invoicing or bookkeeping.

Smart next steps

Formula

Taxable value = Inclusive amount ÷ (1 + GST rate ÷ 100)

GST amount = Inclusive amount − Taxable value

For intra-state supplies the GST amount is split into equal CGST and SGST halves. For inter-state supplies the whole amount is IGST.

Worked example

A customer paid ₹11,800 including 18% GST. Taxable value = 11,800 ÷ 1.18 = ₹10,000, so GST = ₹1,800: CGST ₹900 and SGST ₹900 within the same state.

How to use this calculator

  1. 1Enter the price that already includes GST: an MRP, a cash receipt total or a payment you received.
  2. 2Select the GST rate that applies to that product or service.
  3. 3Read the taxable value and the tax amount worked back out of the total.
  4. 4Use the taxable value for your sales register and the tax for your GST return workings.

When businesses use it

  • Selling at a round MRP and needing the base value to record in your books.
  • Reconciling UPI or cash collections where customers paid the inclusive amount.
  • Checking whether a retailer's 'GST included' claim matches the rate they charged.

When you only know the inclusive amount

Retail India runs on round numbers. A customer pays ₹500 for a haircut, ₹2,000 for a repair or scans a UPI QR for the exact bill total, and nobody writes the tax separately at the counter. Your books, however, need the split: the taxable value feeds turnover and the tax component feeds your output liability. Reverse calculation is the bridge between what the customer paid and what the return expects.

The extraction formula divides rather than subtracts. Dividing the inclusive amount by one plus the rate as a decimal isolates the base; the remainder is tax. At 18% this means the tax is roughly 15.25% of the inclusive figure, not 18% of it, a gap that grows with the slab and quietly distorts a full month of collections if you subtract instead of divide.

This also matters for reconciliation. Payment gateways, marketplaces and card settlements report gross inclusive amounts net of their own commission, so you need the inclusive-to-taxable step before you can match settlement reports with your sales register or explain a GSTR-1 versus GSTR-3B difference to your accountant.

Where reverse GST usually goes wrong

  • Subtracting the rate from the total instead of dividing, which understates the taxable value.
  • Mixing slabs in one day's collections and reversing the whole figure at a single rate.
  • Forgetting that marketplace commission is a separate inward supply with its own GST.
  • Reversing on the amount received after TDS or gateway charges rather than the billed total.

The taxable value you just worked out is what belongs in your GSTR-1, invoice by invoice, not the tax you eventually pay, which is a separate figure worked out in GSTR-3B. See GSTR-1 vs GSTR-3B if you've ever had to explain that difference to your accountant.

Sources & references

The rules behind this calculator, from the official source. Rates and thresholds change — confirm the current figure on the source itself before relying on it for a filing.

Learn the maths behind it

  • How to calculate GST

    Multiply the taxable value by the GST rate to add tax; divide the inclusive price by 1 + rate/100 to remove it.

  • GST 2.0: the new GST rates explained

    From 22 September 2025, GST runs on four slabs (0%, 5%, 18% and a 40% special rate) with most 12% items moving to 5% and most 28% items moving to 18%.

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Frequently Asked Questions

Divide the total by 1.18. For 5% divide by 1.05, and for the 40% special rate on luxury and sin goods divide by 1.40. The difference between the total and that result is the GST. This is the same thing people mean by 'taking GST off' a total, 'subtracting GST' or doing a 'back calculation of GST': always divide by 1 + rate ÷ 100, never subtract the percentage straight off the total.

No. Reverse GST simply extracts tax from an inclusive price. Reverse charge mechanism (RCM) means the recipient pays the GST to the government instead of the supplier.

The taxable value goes in the item row, and CGST/SGST or IGST are shown as separate lines. The inclusive figure becomes the invoice total.

Not in one step. Split the cart by slab first, reverse each portion at its own rate, then add the taxable values together.

Yes. Maximum retail price is legally an all-inclusive price, so the tax inside it must be extracted rather than added on top.

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Calculations happen instantly in your browser. Your calculator inputs aren't sent to our servers. KaroDesk provides calculations and information for general informational purposes. Results should be verified against applicable laws, official notifications, employer policies, lender terms, or professional advice where appropriate. Read our full disclaimer.