GST invoice generator

What has to be on a tax invoice

A GST tax invoice is a compliance document, not just a bill. Section 31 of the CGST Act and the invoice rules require a specific set of fields, and the form above collects each of them:

A missing GSTIN or place of supply is what causes a buyer's input tax credit claim to fail, which is when they come back asking for a corrected invoice.

CGST and SGST, or IGST

It depends on the place of supply, not on where you happen to be sitting.

• Same state as the buyer: the rate splits equally into CGST and SGST. An 18% invoice becomes 9% plus 9%.
• Different state, or an export or SEZ supply: the full rate is charged as IGST.

The tool applies the split automatically once you set the place of supply, so the common error of charging CGST and SGST on an inter-state invoice does not happen.

HSN and SAC codes by turnover

Codes are mandatory, and the required length depends on aggregate turnover:

• Up to ₹5 crore: 4-digit HSN on B2B invoices, optional on B2C.
• Above ₹5 crore: 6-digit HSN on all invoices.

Service providers use SAC codes instead. Most freelance and consulting work falls under the 9983 or 9984 families, but confirm the specific code for what you actually supply rather than copying one from another invoice.

Invoice numbering rules

Numbers must be consecutive and unique within a financial year, at most 16 characters, using letters, numbers and characters like hyphen or slash. Most businesses restart the series each April, for example INV-2026-001.

Two things that cause problems at filing time: skipping numbers, which you then have to explain, and running two parallel series without being able to show why. Pick one series and keep it unbroken.

If you are not registered under GST

You cannot issue a tax invoice or charge GST. You issue a plain invoice with no tax component. Charging GST without a GSTIN is a straightforward compliance problem, not a grey area.

Registration becomes mandatory once your aggregate turnover crosses the threshold for your state and supply type, and there are situations, such as supplying to clients in other states, where it can apply earlier. Businesses under the composition scheme issue a bill of supply rather than a tax invoice and cannot collect GST from customers. GST invoicing for freelancers covers the registration thresholds and the practical rules for consulting income.

Keeping the paperwork straight

Issue the invoice at or before supply, keep a copy for the retention period, and reconcile what you have issued against your GSTR-1 each period. If you also draw a salary alongside freelance income, the income tax calculator handles the salary side, though professional income is taxed under its own head and is worth taking to a CA.