GST invoice checklist: what every invoice must show
Guides · · 4 min read · By Vikram Shah, Solutions, LogAI
A GST invoice is not just a bill. It is the document your customer uses to claim input credit and the record the tax department expects to match against your returns. Get a field wrong and a customer's accountant sends it back; leave one out and you have a problem at filing time.
This checklist covers what a tax invoice has to show under the CGST Rules, in plain words, plus the decisions small businesses most often get wrong. It is a practical guide, not legal advice; your CA has the final say for your situation.
The fields every tax invoice must carry
- Your legal name, address and GSTIN.
- A unique, consecutive invoice number for the financial year, up to 16 characters, using letters, numbers and only the hyphen or slash as special characters.
- The date of issue.
- The customer's name, address and GSTIN if they are registered. For an unregistered customer on a bill above ₹50,000, their name, address and the delivery address and state.
- The HSN code for goods or SAC code for services.
- A description of each item, the quantity and unit, and the total value.
- The taxable value after any discount shown on the invoice.
- The tax rate and the tax amount, split into CGST and SGST for a sale within your state, or IGST for a sale to another state.
- The place of supply with the state name whenever the sale crosses state lines.
- Whether tax is payable on reverse charge.
- A signature or digital signature of you or an authorised person.
CGST and SGST, or IGST?
The rule is about where the goods go or where the service is received, not where the customer's head office is. A sale delivered within your own state is split into CGST and SGST, half and half. A sale delivered to another state is charged as IGST at the full rate. Getting this wrong is the single most common reason a B2B invoice gets rejected, because the customer cannot claim the credit they expected.
How many digits of HSN?
If your aggregate turnover in the previous financial year was up to ₹5 crore, you need a 4-digit HSN code on invoices to registered customers; on invoices to consumers it is optional. Above ₹5 crore you need 6 digits on every invoice. Pick the code once per product and let the software carry it, rather than typing it every time.
Numbering that will not come back to bite you
Invoice numbers must run in sequence through the financial year with no gaps and no repeats. Restart the series on 1 April if you like, with a prefix such as INV/26-27/0001, but never delete an invoice. If a sale is cancelled, issue a credit note against the invoice instead. Keep separate series for different branches or sales channels if that helps, as long as each series is consecutive.
Three cases that are not a tax invoice
- Composition scheme. If you are registered under the composition scheme you issue a bill of supply, not a tax invoice, and you do not charge GST on it.
- Exempt goods or services. These also go on a bill of supply.
- Advance payments. A receipt voucher is issued when you take an advance, and the invoice follows when you supply.
When the invoice has to be issued
For goods, on or before the goods leave your premises or are delivered. For services, within 30 days of providing the service. Issuing late is a compliance issue even if the tax is paid on time.
E-invoicing: who needs it
Businesses whose aggregate turnover crossed ₹5 crore in any financial year since 2017-18 must register B2B invoices on the government's Invoice Registration Portal and print the IRN and QR code on the invoice. If you are under that threshold, a normal tax invoice is enough. LogAI produces GST tax invoices with the correct CGST, SGST and IGST split and HSN codes; it does not generate IRNs, so businesses above the e-invoicing threshold should run invoices through their IRP-connected tool.
The mistakes we see most
| Mistake | Why it matters | Fix |
|---|---|---|
| Charging CGST and SGST on an inter-state sale | Customer cannot claim input credit; invoice gets rejected | Set the place of supply on every customer address |
| Missing or wrong customer GSTIN | Credit does not reflect in the customer's return | Verify the GSTIN once and save it on the customer record |
| Gaps in the invoice series | Looks like a deleted sale during scrutiny | Cancel with a credit note, never delete |
| Discount not shown on the invoice | Tax is due on the full value | Put the discount on the invoice line, before tax |
| Rounded totals that do not match tax lines | Return mismatches | Let the software round once, at the end |
Software should carry most of this for you. In LogAI the GSTIN, address and state live on the customer record, products carry their HSN codes, and the invoice works out the CGST, SGST or IGST split from the place of supply. Numbering runs in series per document type and financial year, and returns raise a credit note instead of deleting anything.
The accountant stopped sending invoices back. That was the whole result, and it was worth it.
Frequently asked questions
What is the difference between a tax invoice and a bill of supply?
A tax invoice charges GST and lets a registered customer claim input credit. A bill of supply is issued for exempt goods or services and by businesses on the composition scheme; it carries no tax.
How many digits of HSN code do I need on a GST invoice?
Four digits if your previous year's turnover was up to ₹5 crore (optional on invoices to consumers), six digits above ₹5 crore.
Can I delete a GST invoice that was issued by mistake?
No. Issue a credit note against it. Invoice numbers must run consecutively with no gaps, so a deleted invoice looks like a missing sale.
Do I need e-invoicing for my small business?
Only if your aggregate turnover crossed ₹5 crore in any year since 2017-18. Below that, a standard GST tax invoice is enough. LogAI issues GST invoices but does not generate IRNs.
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