FactorybookGST invoice format: every field you must include
A tax invoice under GST has to carry a specific set of fields. Miss one and your buyer can't claim input tax credit — which usually means reissuing the invoice. This is the full list, what each field means, and the four mistakes that cause most of the trouble.
The mandatory fields
| Field | What it means |
|---|---|
| Supplier name, address and GSTIN | The issuing business, exactly as registered. |
| Invoice number | Consecutive, unique within the financial year, max 16 characters. Letters, numerals, / and - only. |
| Invoice date | The date of issue. |
| Recipient name, address and GSTIN | GSTIN is required where the buyer is registered. |
| Place of supply | The state. This is what decides IGST versus CGST + SGST. |
| HSN or SAC code | HSN for goods, SAC for services. Digits required scale with turnover. |
| Description, quantity and unit | Per line item. |
| Taxable value | Value after any discount, before tax. |
| Tax rate and amount | Split as CGST + SGST for intra-state, IGST for inter-state. |
| Total invoice value | In figures, and in words where required. |
| Reverse charge indicator | Whether tax is payable on reverse charge. |
| Signature | Physical or digital signature of the supplier or an authorised person. |
How many HSN digits do you need?
This is set by your turnover in the previous financial year, not by what you're selling.
| Annual turnover | HSN digits | Applies to |
|---|---|---|
| Up to ₹5 crore | 4 digits | B2B invoices. Optional on B2C. |
| Above ₹5 crore | 6 digits | All invoices. |
Four mistakes that cause most notices
Breaking the invoice number series
Numbers must run consecutively within the financial year. Restarting mid-year, or leaving gaps when an invoice is cancelled rather than issuing a credit note, is the most common notice trigger.
Wrong place of supply
Charging CGST + SGST on an inter-state supply (or IGST on an intra-state one) means the buyer cannot claim the credit, and you pay the correct tax again.
Too few HSN digits
Turnover above ₹5 crore requires 6 digits. A 4-digit code is an incomplete invoice.
Missing the buyer GSTIN
Without it your registered buyer cannot claim input tax credit, and they will ask for the invoice to be reissued.
Intra-state or inter-state?
Compare the place of supply with the supplier's state. Same state, and you split the tax into CGST and SGST. Different states, and the whole amount is IGST. The rate is the same either way — only the split changes.
- Supplier in Telangana, buyer in Telangana → CGST 9% + SGST 9%
- Supplier in Telangana, buyer in Maharashtra → IGST 18%
Related
Get the fields filled in for you
Factorybook's invoice forms carry GSTIN, HSN/SAC, place of supply and e-way bill fields as standard, and its AI reads a photo of a supplier invoice and fills them in — so the format is handled before you start typing.
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