Use our Discount + GST Calculator to compute GST on discounted prices, net amount, savings and total payable instantly.
Calculate final price after discount and adding GST/tax.
The Discount + GST Calculator is an essential tool for businesses, retailers, and consumers navigating the complexities of tax calculations on discounted goods and services. Goods and Services Tax (GST) is a value-added tax applied at each stage of the supply chain, and understanding how it interacts with discounts is crucial for accurate pricing, invoicing, and tax compliance.
In retail and e-commerce, promotional discounts are ubiquitous—from seasonal sales and clearance events to loyalty programs and bulk purchase incentives. The fundamental principle governing GST on discounts is straightforward: tax is calculated on the actual transaction value, meaning the price after all applicable discounts have been deducted. This ensures consumers pay tax only on what they actually spend, and businesses collect the correct amount of tax for remittance to authorities.
Getting this calculation wrong has real consequences. Overcharging GST leads to customer complaints and potential refund obligations, while undercharging creates tax liabilities during audits. This calculator eliminates guesswork by applying the correct sequence: discount first, then tax—giving you accurate final prices every time.
Example: Original Price = ₹1,000, Discount = 20%, GST = 18%
Discounted Price = ₹1,000 × (1 - 0.20) = ₹800
GST Amount = ₹800 × 0.18 = ₹144
Final Price = ₹800 + ₹144 = ₹944
See how different discount levels affect final prices and tax amounts:
| Original Price | Discount % | Discounted Price | GST (18%) | Final Price | You Save |
|---|---|---|---|---|---|
| ₹1,000 | 10% | ₹900 | ₹162 | ₹1,062 | ₹118 |
| ₹1,000 | 20% | ₹800 | ₹144 | ₹944 | ₹236 |
| ₹1,000 | 30% | ₹700 | ₹126 | ₹826 | ₹354 |
| ₹5,000 | 25% | ₹3,750 | ₹675 | ₹4,425 | ₹1,475 |
| ₹10,000 | 15% | ₹8,500 | ₹1,530 | ₹10,030 | ₹1,770 |
Note: "You Save" includes both discount savings and reduced GST compared to full-price purchase.
Different discount types have specific GST treatment requirements:
Trade Discounts: Deducted directly from taxable value. Must be mentioned on the invoice at the time of supply. Common in B2B transactions where volume or loyalty-based discounts apply. GST is calculated on net amount after trade discount.
Cash Discounts: Offered for early/prompt payment (e.g., "2% discount if paid within 10 days"). Under GST law, these do NOT reduce taxable value—GST is calculated on the full invoice amount. The cash discount is treated as a separate financial transaction.
Promotional Discounts: Sale prices, clearance discounts, and seasonal offers reduce taxable value if clearly stated at point of sale. BOGO (Buy One Get One) offers apply GST to the effective per-item price.
Post-Sale Rebates: If discounts are provided after the sale (volume rebates, year-end incentives), the supplier must issue a credit note and adjust GST accordingly in their returns.
❌ Calculating GST on original price: This overcharges customers and creates excess tax liability. Always calculate GST on the post-discount amount.
❌ Not documenting discounts on invoice: Undocumented discounts may be disallowed during tax audits. Clearly show original price, discount amount, and taxable value on every invoice.
❌ Confusing cash discounts with trade discounts: Cash discounts (for early payment) don't reduce GST liability; trade discounts (at point of sale) do. Treating them the same causes filing errors.
❌ Applying discount after GST: The correct order is discount first, then GST. Reversing this inflates the tax amount incorrectly.
❌ Ignoring input tax credit adjustments: When you receive a discount on purchases, remember to proportionally reduce your input tax credit claim.
Common tax rates for reference—always verify current rates with local tax authorities:
| Country/Region | Tax Type | Standard Rate | Reduced Rates |
|---|---|---|---|
| India | GST | 18% | 5%, 12%, 28% |
| Australia | GST | 10% | 0% (essentials) |
| Canada | GST/HST | 5-15% | Varies by province |
| Singapore | GST | 9% | 0% (exports) |
| United Kingdom | VAT | 20% | 5%, 0% |
| European Union | VAT | 17-27% | 5-15% |
Sources & Disclaimer: GST treatment of discounts is governed by Section 15 of the CGST Act, 2017 (India), A New Tax System (Goods and Services Tax) Act 1999 (Australia), and Excise Tax Act (Canada). Tax rates and rules are subject to change—always consult current legislation and tax professionals for compliance. This calculator provides estimates for educational purposes and should not substitute professional tax advice. Last updated January 2026.
To calculate GST on discounted products, first apply the discount to the original price (Original Price × (1 - Discount %)), then calculate GST on the discounted amount (Discounted Price × GST Rate). For example, a ₹1,000 item with 20% discount becomes ₹800, then 18% GST adds ₹144, making the final price ₹944. Always calculate GST on the post-discount price—this is the legally correct method followed by tax authorities worldwide including India's CBIC, Australia's ATO, and Canada's CRA.
GST is always calculated AFTER the discount is applied. According to GST law, the taxable value is the transaction value—the actual price paid after all discounts. If you sell a ₹1,000 product at 20% off, GST applies to ₹800, not ₹1,000. This rule applies to trade discounts, promotional discounts, and volume discounts as long as they're clearly stated on the invoice. Calculating GST on the original pre-discount price is a common mistake that leads to overcharging customers and potential compliance issues.
Promotional discounts are fully deductible from taxable value if properly documented. The discount must be known at the time of supply and recorded on the invoice. For 'Buy One Get One Free' offers, GST applies to the effective price paid (full price ÷ 2 per item). Cash discounts for early payment are treated differently—GST is calculated on the full invoice amount, and the discount is a separate financial transaction. Trade discounts given at point of sale reduce the taxable value directly, while post-sale rebates may require credit note adjustments.