GST Invoice Calculator
Build an invoice value from quantity, rate, discount and GST — line by line.
Enter quantity and rate to build the invoice value.
How the calculation works
An invoice line is built in a fixed order: gross value first, discount second, tax last. Follow the same order and your totals will always tie out.
- Gross value
Quantity × Rate per unit - Taxable value
Gross value − Trade discount - GST
Taxable value × Rate ÷ 100 (split CGST/SGST or IGST) - Line total
Taxable value + GST
Worked example
10 units at ₹1,200 with a 5% trade discount, taxed at 18% intra-state.
You enter
You get
Important points to keep in mind
- Every invoice needs the buyer's GSTIN (for B2B), your GSTIN, invoice number/date, HSN codes and the tax split shown separately.
- Trade discounts must appear on the invoice itself to be excluded from taxable value.
- For multi-item invoices at different slabs, use the Invoice Total tool instead.
Frequently asked questions
Should GST be calculated per line or on the invoice total?
Per line, then summed — especially when lines carry different rates or supply types. This tool mirrors that behaviour for a single line.
Do I charge GST on shipping?
Freight billed on the same invoice generally becomes part of the transaction value and attracts GST at the rate of the goods being moved.
What about rounding?
Round each line to the nearest paise; the invoice's 'round off' line absorbs any final odd amount.
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.