A GST invoice is a tax invoice that a GST-registered business must issue for every taxable sale of goods or services in India. It shows the seller's and buyer's GSTINs, a unique invoice number and date, HSN or SAC codes, quantity, taxable value, the GST rate and the tax split into CGST and SGST or IGST.
Why it matters for an Indian small business
The invoice is the document that lets your customer claim input tax credit, so a missing field or a wrong GSTIN means a B2B buyer cannot recover the tax and will push back or stop ordering. It is also what the GST return is built from: every invoice must be reported in GSTR-1, and mismatches between your invoices and your customer's claims trigger notices. For businesses above ₹5 crore turnover, B2B invoices must also be registered on the e-invoice portal to get an IRN and QR code before issue.
Done right, the invoice is a sales tool: a clean, numbered, GST-compliant invoice with UPI payment details gets paid faster than a handwritten bill.
How it works
Mandatory contents include the supplier's name, address and GSTIN; a consecutive invoice number unique to the financial year; date; the recipient's name, address and GSTIN if registered; place of supply with state code; HSN code for goods or SAC code for services; description, quantity and unit; taxable value after discounts; rate and amount of CGST and SGST for intra-state sales or IGST for inter-state; total; whether tax is payable on reverse charge; and a signature or digital signature.
Invoices for goods are issued at or before delivery; for services within 30 days. Registered sellers under the composition scheme issue a bill of supply instead, and sales to unregistered customers under ₹200 can go on a consolidated daily invoice. Keep copies for six years from the return due date.
Example: a Nagpur orange exporter
Vidarbha Citrus sells graded oranges to wholesalers in Delhi and to a juice maker in Pune. The Pune sale is intra-state, so the invoice shows CGST 2.5 percent and SGST 2.5 percent on the taxable value of ₹1,80,000. The Delhi sale is inter-state, so the invoice shows IGST 5 percent with place of supply 07. Both carry the HSN code 0805, the buyer's GSTIN, a sequential number like VC/2026-27/0147, and a UPI QR for payment. When the Pune buyer files GSTR-2B, the credit appears cleanly, and the exporter's accountant uploads the invoices to GSTR-1 without a single mismatch that quarter.
Common mistakes
- Using one invoice number series that restarts or skips, which is non-compliant.
- Charging IGST on an intra-state sale or CGST and SGST on an inter-state one.
- Missing the buyer's GSTIN on a B2B invoice, so they lose credit.
- Wrong HSN digits for your turnover band.
- Issuing invoices from a word processor with totals that do not reconcile with returns.
How Neweb handles it
Neweb issues GST-compliant invoices for its own subscriptions with its GSTIN and SAC code, and its free GST invoice generator produces compliant invoices for your sales with automatic CGST, SGST or IGST calculation, sequential numbering and an optional UPI QR.
GST Invoice questions
What fields are mandatory on a GST invoice?
Supplier and buyer details with GSTINs, unique sequential invoice number and date, place of supply, HSN or SAC codes, description and quantity, taxable value, GST rate, CGST and SGST or IGST amounts, total, reverse charge note and signature.
When is CGST and SGST charged versus IGST?
CGST plus SGST apply when supplier and place of supply are in the same state. IGST applies for inter-state supplies, imports and supplies to SEZ units.
Can I issue a GST invoice without a GSTIN?
No. Unregistered businesses issue ordinary bills without GST. Charging GST without registration is an offence.
Is e-invoicing mandatory for small businesses?
E-invoicing applies to businesses with aggregate turnover above ₹5 crore for B2B and export invoices. Smaller businesses issue normal GST invoices without an IRN.
How long must I keep GST invoices?
At least 72 months from the due date of the annual return for that year, in physical or digital form.
Related terms.
Related pages.
GST invoice generator
Create compliant invoices with automatic tax split and numbering.
Common GST invoice mistakes
The errors that cost buyers their input credit.
Invoice number generator
Set up a compliant sequential series for the financial year.
E-invoicing rules 2026
Thresholds, IRN and QR code requirements explained.
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