If you're registered under GST in India, your invoices are more than a payment request — they're the document your client uses to claim input tax credit, and the record your GST returns are built from. That means a GST invoice has to carry a specific set of fields, in a format your client's accountant can reconcile without calling you. Here's what a GST invoice typically includes and how B2B invoices differ from B2C ones.
The fields a GST invoice typically carries
A compliant GST invoice commonly includes:
- Your GSTIN — the 15-character registration number of the supplier (issued through the official GST portal), alongside your legal business name and address.
- The recipient's GSTIN — for B2B supplies, the client's GSTIN appears too. Without it, the client generally can't claim input tax credit against your invoice.
- A sequential invoice number — unique for the financial year, part of a consecutive series. Gaps and duplicates are what auditors look for first, so pick one series and stick to it.
- Invoice date — the date of issue, which drives which tax period the invoice falls into.
- HSN or SAC codes — HSN codes classify goods, SAC codes classify services. Each line item carries the relevant code; how many digits you need typically depends on your turnover band.
- Description, quantity, and value of each line — plus the taxable value after any discount.
- The tax breakup — GST is commonly split into CGST + SGST for supplies within a state, or shown as IGST for supplies across states. The rate and amount for each component appear separately, not buried in the line price.
- Place of supply — especially relevant for inter-state supplies, since it determines whether CGST/SGST or IGST applies.
- Signature or digital signature of the supplier, where required.
The structural idea behind all of this: anyone reading the invoice can tell who supplied what, to whom, under which registration, and exactly how much tax was charged at which rate.
B2B vs B2C: what changes structurally
The core difference is the recipient's GSTIN and the level of detail it drives.
| Element | B2B invoice | B2C invoice |
|---|---|---|
| Recipient GSTIN | Shown — client needs it for input credit | Not applicable (customer unregistered) |
| Recipient name/address | Full details | Commonly required only above a value threshold |
| Tax breakup | Itemized (CGST/SGST or IGST, rate + amount) | Shown, though small-value B2C sales may use a consolidated or simplified format |
| Stakes if wrong | Client's input credit is blocked | Mostly your own filing accuracy |
In practice, B2B clients scrutinize invoices harder because their money is on the line: a missing GSTIN or wrong place of supply can block their credit claim, and their finance team will bounce the invoice back to you. B2C invoices matter mainly for your own returns.
Numbering and series discipline
GST invoice numbers are expected to be consecutive and unique within a financial year. A common pattern is a prefix plus a resetting sequence — INV/2026-27/001 and counting up. Whatever format you choose, don't reuse numbers, don't skip around, and don't run parallel series for the same registration unless you're tracking them deliberately (say, separate series per branch).
A worked example
Here's what a typical inter-state B2B services invoice looks like, with GSTINs for both parties, a SAC reference in the description, and IGST shown as a single labeled rate:
Example: inter-state B2B services invoice with GST
A Bengaluru design studio billing a Mumbai client. Both GSTINs shown, SAC code noted per line, IGST applied at a single labeled rate.
On an intra-state invoice, you'd instead present the same total tax split into CGST and SGST components — in InvoiceKo, choose the "GST (CGST + SGST)" tax type and the invoice splits your rate equally into the two labeled lines automatically. The generator also carries dedicated fields for HSN/SAC codes per line, place of supply, and the reverse-charge declaration.
Common mistakes that get invoices bounced
- Missing or mistyped client GSTIN on a B2B invoice — the single most common reason a finance team rejects an invoice.
- Wrong place of supply, leading to CGST/SGST charged where IGST applied (or the reverse).
- Tax folded into line prices with no separate breakup — the rate and amount need to be visible.
- Broken number sequences from ad-hoc numbering across notebooks, spreadsheets, and tools.
InvoiceKo's GST invoice generator handles the structure for you: GST as the tax label at any rate, tax ID fields for both parties, sequential numbering, INR among 25+ currencies, and a clean PDF with no watermark or signup. If you also invoice clients abroad, see how to show tax on an invoice for how GST, VAT, and sales tax presentation compare.
Official references: the GST portal for registration and returns, and the Central Board of Indirect Taxes and Customs (CBIC) for the underlying rules and notifications.
Tax rules vary and change — confirm the specifics with your accountant or local tax authority.