A valid GST tax invoice must carry a set of details laid down in Rule 46 of the CGST Rules: supplier and recipient details with GSTINs, a unique serial number and date, HSN or SAC codes, description, taxable value, tax rate and amount, place of supply and a signature. Miss one and your customer may struggle to claim input tax credit — and for exporters, the invoice is the same document your EDF, GST return and bank matching all rely on.
Key takeaways
- Rule 46 lists the mandatory contents of a tax invoice; most are simple but easy to get slightly wrong.
- Invoice numbers must be consecutive, unique for the financial year and not longer than 16 characters.
- Place of supply decides CGST + SGST versus IGST — and, for exports, whether the supply is zero-rated.
- Export invoices need extra wording, the recipient's address abroad and the country of destination.
- Businesses above the e-invoicing threshold must also generate an IRN; check the current threshold with your CA.
The mandatory fields at a glance
| # | Field | What it means in practice |
|---|---|---|
| 1 | Supplier name, address and GSTIN | Exactly as on your GST registration |
| 2 | Invoice number | Consecutive, unique in the financial year, up to 16 characters; letters, numbers, hyphen and slash allowed |
| 3 | Invoice date | Date of issue |
| 4 | Recipient name, address and GSTIN | GSTIN if the recipient is registered |
| 5 | Delivery address and state, for some unregistered recipients | Required in specified cases; check with your CA |
| 6 | HSN or SAC code | HSN for goods, SAC for services; digits depend on turnover |
| 7 | Description | Clear description of goods or services |
| 8 | Quantity and unit | For goods |
| 9 | Total value | Full value of the supply |
| 10 | Taxable value | After discounts |
| 11 | Tax rate | CGST, SGST/UTGST, IGST and cess as applicable |
| 12 | Tax amount | For each tax head |
| 13 | Place of supply with state name | For inter-state supplies |
| 14 | Delivery address if different from place of supply | Where applicable |
| 15 | Reverse charge indication | Whether tax is payable on reverse charge |
| 16 | Signature | Physical or digital signature of supplier or authorised representative |
This summary is for orientation. The rule's exact text and any later amendments govern, and this is general information, not legal or tax advice.
Getting the tricky fields right
Invoice number
The 16-character limit catches businesses with long prefixes. "NIMBUSLABS/2026-27/INV/0001" is too long; "NL/26-27/0001" works. Restart or continue series each financial year as you choose, but never reuse a number in the same year. Keep a separate series for export invoices if it helps you find them quickly.
HSN or SAC
Goods use HSN codes; services use SAC codes beginning with 99. The number of digits you must show depends on your aggregate turnover in the previous year — businesses above ₹5 crore generally show six digits. If you're unsure, our HSN vs SAC explainer and the SAC code finder help.
Place of supply and tax type
Place of supply decides the tax:
- Same state as supplier → CGST + SGST (or UTGST).
- Different state → IGST.
- Outside India (exports) → zero-rated, either under LUT with no IGST, or with IGST paid and refunded.
Getting this wrong is the most common reason invoices need to be cancelled and reissued. Our guide to choosing CGST, SGST or IGST walks through examples.
Extra fields on an export invoice
Export invoices carry everything above, plus:
- Export wording. Under LUT: "Supply meant for export under LUT without payment of IGST". With IGST paid, wording stating the supply is for export on payment of IGST.
- Recipient's name and full foreign address.
- Country of destination.
- Currency and amount, with an INR value for GST reporting.
- Bank details for the foreign payment, including SWIFT code.
Export of services is zero-rated under Section 16 of the IGST Act if the Section 2(6) conditions are met: supplier in India, recipient outside India, place of supply outside India, payment in convertible foreign exchange (or INR where RBI permits), and supplier and recipient not merely establishments of a distinct person.
Worked example: a domestic and an export invoice side by side
Asha Design Studio, Kochi (Kerala), issues two invoices on 12 November 2026.
| Field | Domestic invoice | Export invoice |
|---|---|---|
| Invoice no. | ADS/26-27/0142 | ADS/26-27/0143 |
| Recipient | Malabar Foods Pvt Ltd, Bengaluru, GSTIN 29XXXXX | Larkspur Bakeries Ltd, Manchester, UK |
| SAC | 998393 | 998393 |
| Taxable value | ₹1,20,000 | GBP 2,000 (₹2,20,000) |
| Place of supply | Karnataka (29) | Outside India |
| Tax | IGST 18% = ₹21,600 | Nil — under LUT |
| Invoice total | ₹1,41,600 | GBP 2,000 |
| Special wording | — | "Supply meant for export under LUT without payment of IGST" |
The export invoice then appears in GSTR-1's export table and as a row on Asha's November EDF, due 30 December 2026. One document, three uses.
E-invoicing
Businesses with aggregate turnover above the notified e-invoicing threshold must report B2B and export invoices to the Invoice Registration Portal and get an IRN and QR code. The threshold has been lowered over time, so confirm the current figure with your CA. Ask your CA how the e-invoicing rules treat your export invoices.
Common mistakes
| Mistake | Consequence | Fix |
|---|---|---|
| Missing recipient GSTIN on a B2B invoice | Customer can't claim credit easily | Collect GSTIN before invoicing |
| Wrong state in place of supply | Wrong tax type charged | Check the recipient's state code |
| Number longer than 16 characters | Non-compliant numbering | Shorten the prefix |
| Export invoice without LUT wording | Questions on zero-rating | Use a template that adds it |
| No signature on a PDF invoice | Invoice incomplete | Add a digital or scanned signature as permitted |
Our GST invoice generator builds invoices with all these fields, and the export invoice generator adds the export-specific lines.
Frequently asked questions
Which rule sets out the GST invoice format?
Rule 46 of the CGST Rules lists the mandatory contents of a tax invoice. Check the current text with your CA, as rules are amended from time to time.
How long can a GST invoice number be?
Up to 16 characters, using letters, numbers, hyphens and slashes. Numbers must be consecutive and unique for the financial year.
Is a signature mandatory on a GST invoice?
The rule requires a signature or digital signature of the supplier or an authorised representative. For e-invoices, specific provisions apply; ask your CA how they affect you.
What extra details does an export invoice need?
Export wording (for example, "Supply meant for export under LUT without payment of IGST"), the recipient's foreign address, the country of destination, currency and amount, and bank details for payment.
Do I need to show HSN or SAC codes on every invoice?
Yes, at the digit level your turnover requires. Goods use HSN codes and services use SAC codes. Confirm the right code and digits with your CA.
Bottom line
A compliant GST invoice is a checklist, not a design choice — and for exporters it feeds GSTR-1 and the EDF too. Use the free GST invoice generator so every mandatory field is in place from the start.
This guide is general information for Indian businesses, not legal or tax advice. Rules and bank processes change — confirm specifics with your AD bank or chartered accountant.