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About this tool
Apply single or stacked percentage and flat discounts, add GST, and see the true saving and equivalent single discount.
Successive discounts multiply rather than add: a price cut of 20% followed by a further 10% leaves 0.8 × 0.9 = 0.72 of the original, an equivalent single discount of 28% and not 30%. This calculator applies percentage and flat-rupee discounts in the order a checkout actually applies them, adds GST on the discounted value as section 15(3)(a) of the CGST Act requires, and reports the true saving, the final payable amount and the equivalent single discount. It also works backwards from a marked price and a price paid to the discount percentage that implies.
Open Discount and Final Price Calculator on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Percentages are multiplied, not added, and the overstatement is shown explicitly.
Flat and percentage discounts are applied in sequence, because swapping them changes the price.
Tax is computed on the discounted transaction value, matching invoice-level discount rules.
Multiply the remaining fractions rather than adding the discounts. For 20% then 10%, multiply the price by 0.80 and then by 0.90, giving 0.72 of the original — a 28% total discount. On a Rs 2,000 item that is Rs 1,440, so the saving is Rs 560 and not the Rs 600 that adding the percentages would suggest.
No, and the gap widens as the discounts get bigger. Stacking 20% and 10% gives 28%; stacking 50% and 50% gives 75%, not 100%. The equivalent single discount is always 1 − (1 − d₁)(1 − d₂), which is smaller than d₁ + d₂ whenever both are positive.
After, when the discount appears on the invoice itself. Section 15(3)(a) of the CGST Act, 2017 allows a discount given at or before the time of supply and recorded on the invoice to be excluded from the transaction value, so GST applies to the discounted amount. Discounts agreed after the sale need a prior agreement and a credit note before they can reduce the taxable value.
Yes. Taking Rs 200 off Rs 1,000 and then 10% leaves Rs 720, while applying 10% first and then Rs 200 off leaves Rs 700 — a Rs 20 difference on the same two offers. Percentage discounts commute with each other, but a flat amount does not commute with a percentage, so enter the steps in the order the seller applies them.
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