GST Invoice Value Calculator

Calculate complete GST invoice value with gross amount, trade discount, CGST + SGST or IGST, and final invoice total. For B2B and B2C billing.

GST Invoice Value Calculator

Build a complete GST invoice — taxable value, discount, CGST/SGST or IGST

Gross value (before discount) Rs 1,00,000
Rs 1,000Rs 1Cr
Rs
Trade discount 0%

Discount shown on invoice — GST is not charged on this amount

0%50%
%
GST rate
0%28%
%
Supply type
Invoice total
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incl. GST
Taxable value
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after discount
Total GST
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CGST + SGST
Gross value---
Trade discount---
Net taxable value---
CGST (9%)---
SGST (9%)---
Invoice total---
Taxable value vs GST
Taxable: ---
GST: ---

GST on invoices per CGST Act 2017. E-invoicing mandatory for turnover above Rs 5 crore.

Invoice value breakdown
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ThriftRupee Insight

A common invoicing mistake: applying GST on the gross amount before deducting trade discount. GST must be levied on the post-discount net value. Charging GST on pre-discount price inflates tax liability and reduces the buyer's ITC claim. Formula: Net value = Gross − Discount → GST on net value only.

GST Invoice Value Calculator — How to Build a GST Invoice

A GST invoice must show the taxable value, applicable GST (CGST + SGST for intra-state, IGST for inter-state), and the total invoice amount. Trade discounts shown on the invoice are deducted before computing GST. This calculator builds a complete invoice summary instantly.

GST invoicing rules in India (2026)

Tax invoices must be issued for all taxable supplies. For B2B supplies, the buyer's GSTIN is required. For B2C supplies over Rs 2.5 lakh (inter-state), a tax invoice is mandatory. HSN codes are required for goods and SAC codes for services. Businesses with turnover above Rs 5 crore must generate an e-invoice (IRN) from the IRP before issuing to the buyer.

Frequently asked questions

How is GST calculated on a sales invoice?▼
Invoice GST = (Gross Amount − Trade Discount) × GST rate. For intra-state supplies, split into CGST + SGST at half rate each. For inter-state, charge IGST at the full rate. The final invoice value = net taxable value + total GST.
Is GST charged on trade discounts?▼
No. Trade discounts deducted at the time of supply are excluded from the taxable value — GST applies only on the net amount after discount. However, post-sale discounts not shown on the invoice require a credit note with GST adjustment.
What details are mandatory on a GST tax invoice?▼
A valid GST invoice must include: supplier GSTIN, invoice number and date, buyer GSTIN (for B2B), HSN/SAC code, description of goods/services, taxable value, applicable GST rates (CGST+SGST or IGST), and total invoice amount. B2B invoices above Rs 5 crore also need an e-invoice (IRN).
When is e-invoicing mandatory?▼
E-invoicing under GST is mandatory for businesses with aggregate turnover above Rs 5 crore (from August 2023). It requires generating an Invoice Reference Number (IRN) from the GST portal's Invoice Registration Portal (IRP) before issuing the invoice to the buyer.

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