GST invoice checklist for small businesses
A tax invoice is more than a bill. Your buyer may use it to claim input tax credit, your CA uses it to prepare returns, and in a dispute it is the record of what was sold and for how much. A missing GSTIN or a wrong state can cost your customer their credit and cost you a phone call, a corrected invoice and some goodwill. This checklist covers the details a GST tax invoice is generally expected to carry and the mistakes small businesses make most often.
This is general guidance, not tax advice. GST rules and rates change; confirm specifics for your business — especially rates, HSN/SAC codes and any e-invoicing requirement — with your chartered accountant or the official GST portal.
The checklist
About you (the supplier)
- Legal name, as on your GST registration (and trade name if you use one)
- Full address
- Your GSTIN
About the invoice
- The words “Tax Invoice” at the top
- An invoice number that is unique for the financial year and runs in sequence. It can contain letters, numbers, hyphens or slashes (for example KP/25-26/0142) and is limited to 16 characters.
- Date of issue
About the buyer
- Name and address
- GSTIN, if the buyer is registered (essential for them to claim credit)
- For an unregistered buyer, name, address and state are expected when the invoice value is ₹50,000 or more
About what you sold
- Description of goods or services
- HSN code (goods) or SAC code (services), to the number of digits that applies to your turnover
- Quantity and unit (Nos, Kg, Mtr…)
- Rate, total value, any discount, and the taxable value after discount
About the tax
- Rate and amount of tax, shown separately as CGST + SGST/UTGST for a sale within the same state or UT, or IGST for a sale to another state
- Place of supply, with the state name, for inter-state supplies
- Whether tax is payable on reverse charge, where that applies
- Invoice total in figures (and usually in words)
Finishing
- Signature or digital signature of the supplier or an authorised person
- Bank or UPI details for payment and a due date — not required by GST, but they get you paid faster
Worked example: same state vs another state
A Chandigarh printer bills ₹20,000 of printing work at 18%. To a client in Chandigarh, tax is split as CGST 9% (₹1,800) + UTGST 9% (₹1,800) because Chandigarh is a Union Territory. To a client in Mohali, Punjab, it is an inter-state supply: IGST 18% (₹3,600), with place of supply “Punjab”. The total is ₹23,600 either way; only the split changes. Getting the split wrong is one of the most common reasons an invoice has to be reissued.
Mistakes worth catching before you send
- Wrong or missing buyer GSTIN. Copy it from the buyer’s own document, not from memory, and check all 15 characters.
- CGST/SGST used for an out-of-state buyer (or IGST for a local one). Check the buyer’s state against yours.
- Duplicate or skipped invoice numbers. Let your billing software number invoices instead of typing numbers by hand.
- Rate applied to the wrong value. Tax is calculated on the taxable value after discount.
- Editing a sent invoice. Once issued, corrections are usually made through a credit note or debit note rather than silently changing the original.
- Rounding differences. Make sure line tax amounts add up to the total tax shown.
- Missing HSN/SAC. Keep a short list of the codes you use most and save them with each item.
Related documents you will also need
- Credit note — when goods are returned or you reduce the price after invoicing.
- Debit note — when you need to increase the amount after invoicing.
- Bill of supply — used instead of a tax invoice for exempt supplies or by composition dealers, who cannot charge GST.
- Payment receipt — confirms the money you received against an invoice.
Keeping records tidy
Keep every invoice — including cancelled ones — in one place, sorted by financial year. Record payments against invoices as they arrive, so you always know who owes what. At month end, share the invoice list with your CA instead of a pile of photos. If you are setting this up from scratch, C Invoice raises GST sales invoices, issues credit notes and payment receipts, and keeps a party ledger; it does not file returns. CA practices that receive these records from clients can use C Accounts.
Frequently asked questions
Do I need to issue a GST invoice for every sale?
Registered businesses issue a tax invoice for taxable supplies, though there are simplified rules for small retail (B2C) sales. Ask your CA which applies to you.
Can I handwrite invoices?
Handwritten invoices can be valid if they contain the required details, but software reduces numbering and calculation mistakes and makes records easier to share.
What is e-invoicing?
Businesses above a notified turnover limit must report B2B invoices to the government’s Invoice Registration Portal. Check the current limit with your CA; most very small businesses are not covered.