A GST tax invoice is not just a receipt. It is the document your buyer uses to claim input tax credit, and the one an officer reads first. Rule 46 of the CGST Rules, 2017 lists what it must say. Here is that list in plain words.
Who you are, and who is buying
- Your name, address and GSTIN.
- The buyer’s name, address and GSTIN, if the buyer is registered.
- For an unregistered buyer, when the invoice is worth ₹50,000 or more: their name and address, the delivery address, and the name and code of their state.
The invoice itself
- A serial number — consecutive, at most 16 characters, made of letters, numbers, hyphens or slashes, and unique for the financial year. You may run more than one series (say, one per counter), but no number may repeat within a year.
- The date of issue.
- Place of supply, with the state’s name, for a sale to another state.
- The delivery address, if it differs from the place of supply.
- Whether tax is payable on reverse charge.
Each line
- Description of the goods or services.
- HSN code for goods, or SAC for services. How many digits depends on your turnover in the previous year: businesses up to ₹5 crore must show at least 4 digits on invoices to registered buyers; above ₹5 crore, 6 digits on every invoice.
- Quantity and unit (for goods).
- Total value, and the taxable value after any discount.
- The rate and amount of tax, under each head charged — CGST and SGST (or UTGST) for a sale within your state, IGST for one to another state — plus cess if it applies.
Signing it
The invoice carries the signature or digital signature of the supplier or someone authorised by them. An e-invoice issued through the Invoice Registration Portal does not need one.
What about e-invoicing?
Businesses whose aggregate turnover has crossed ₹5 crore in any financial year since 2017–18 must report B2B invoices to the Invoice Registration Portal and print the IRN and QR code it returns. Below that threshold, a normal tax invoice is enough.
Three mistakes we see
- Gaps or repeats in numbering — usually from two people billing on two machines from one series.
- The wrong tax heads — CGST and SGST on a sale to another state, or IGST on a local one.
- One GST rate for the whole bill, when the items on it are taxed at different rates.
How Billyng helps — and where it doesn’t yet
Billyng numbers invoices consecutively for each GST number, picks CGST + SGST or IGST from the two state codes, and taxes every line at its own product’s rate. It does not yet record HSN codes against products, and it does not generate e-invoices (IRN) — if you need either, plan for it before you switch.
This article summarises the rules for general guidance. Check the current notifications on the CBIC site, or ask your tax adviser, for your own case.