GST Discount Calculator
Apply trade discounts before tax and see why order matters for GST.
Enter a list price and discount to see the invoice-ready value.
How the calculation works
GST law taxes the value actually billed after discount. Applying the discount before tax therefore changes the GST you collect — this shows both methods side by side.
- Discount amount
List price × Discount % ÷ 100 - Correct taxable value
List price − Discount (tax applies here) - GST
Taxable value × Rate ÷ 100
Worked example
₹20,000 list price, 10% discount, 18% GST.
You enter
You get
Taxing first and discounting after would bill ₹21,420 — ₹180 more, and wrongly so.
Important points to keep in mind
- The discount must be recorded on the invoice; verbal discounts don't reduce taxable value.
- Post-sale discounts given through credit notes adjust tax via the credit note mechanism instead.
- Seasonal 'buy one get one' offers are valued per valuation rules — ask your adviser for unusual schemes.
Frequently asked questions
Is discount added before or after GST?
Before. GST is charged on the net value after discounts shown on the invoice, per Section 15 of the CGST Act.
Does a cash discount taken at payment time reduce GST?
No. Only discounts established before or at the time of supply and shown on the invoice reduce taxable value.
Related GST tools
Prepare your returns in GSTSelf
Done estimating? Prepare the actual return.
GSTSelf walks you through your invoices, builds GSTR-1 and GSTR-3B data, and keeps everything on your device — no uploads, no account.