What a GST Tax Invoice Must Legally Contain (And What Quietly Blocks Your Buyer's Credit)

When someone asks what a GST invoice should look like, they are almost never asking about layout. They are asking a different question without realising it: will my buyer be able to claim credit on this, or will it come back to me in three weeks? That is the question worth answering, because an invoice that is beautiful and incomplete costs you more than an ugly one that is correct.

The law does not prescribe a design. Rule 46 of the CGST Rules lists particulars a tax invoice must carry, and leaves the arrangement to you. You can put your logo where you like. What you cannot do is leave a particular out.

The particulars nobody disputes

Published checklists disagree on how many fields Rule 46 contains — you will see sixteen, seventeen and twenty-one, depending on how the writer groups the sub-clauses, and the rule itself has been amended more than once. Rather than repeat a number that may not match the current text, here are the particulars that every reading agrees on. For the authoritative list, read the current Rule 46 on the CBIC site, or ask your CA to confirm it against the version in force.

• Your name, address and GSTIN. The legal name as registered, not the trading name you use on WhatsApp.
• A serial number unique within the financial year, up to sixteen characters. Unique within the year is the part people miss — restarting your series in April is normal and expected.
• The date of issue.
• The recipient's name, address and GSTIN where they are registered. For unregistered buyers above the prescribed value, the name, address, delivery address, and the State with its code.
• A description of the goods or services, the quantity where it applies, and the taxable value after any discount.
• The HSN or SAC code for what you sold.
• The rate and the amount of tax, split as CGST and SGST, or as IGST, according to whether the supply is intra-State or inter-State.
• The words "Tax Invoice" on the face of it. A proforma or an estimate is not a tax invoice and cannot be treated as one.
• Place of supply, and a delivery address where it differs.
• Whether tax is payable under reverse charge.
• A signature or digital signature.

The three that actually cause arguments

Place of supply decides the tax, not the buyer's billing address. Get it wrong and you have charged CGST and SGST where IGST was due, or the reverse. Your buyer's accounts team will notice, because their credit depends on it.

The legal name has to match the registration. "Sharma & Co." on the invoice against "Sharma and Company" on the GSTIN is the kind of mismatch that gets an invoice returned by a large buyer's automated check, and it is invisible to you until it happens.

The series has to be genuinely unique. Two invoices sharing a number in one financial year is a real problem, and it happens most often where numbers are typed by hand or kept in a spreadsheet that two people edit.

Who does not need to worry about most of this

If you are not registered under GST, you do not issue tax invoices at all — you issue a bill of supply, and none of the tax particulars apply. If you sell only to consumers, your buyer is not claiming credit, so the commercial pressure behind all of this disappears; you still have to comply, but nobody is going to bounce your invoice. And if you are under the composition scheme, your document is different again. Half the anxiety about invoice formats belongs to people the rules do not apply to in that form.

A test you can run this week

Take the last ten invoices you issued. For each one, check four things: does the legal name match the GSTIN exactly; is the place of supply right for where the service was actually delivered; is the tax split the right way round; and is the number unique in this financial year. If more than one of the ten fails, the problem is not carelessness — it is that the invoice is being assembled by hand each time, and a number typed by hand will eventually be typed twice.

That is the real argument for software here, and it is a narrow one. A system that allocates the number, holds the GSTIN, and decides the tax split from the place of supply removes the three failure modes above without anyone remembering to be careful. Grovia does that, and so do several others; what matters is that something does.

Grovia is a business platform built for Indian service companies — invoicing, GST reporting, projects, collections and field work in one place. Start a free trial and see whether it fits the way you already work.

Frequently Asked Questions

Is there an official GST invoice format I must use?

No. The law prescribes particulars, not a layout. Any format is acceptable as long as every applicable particular is present and correct, which is why two compliant invoices can look nothing alike.

What happens if a mandatory field is missing?

The practical consequence is usually your buyer's input tax credit, which is why they, rather than the department, are the ones who contact you. There are penalty provisions as well, but the commercial friction arrives first.

Can I restart my invoice numbers in April?

Yes. The requirement is that the number is unique within the financial year, so a fresh series each year is normal practice. What you must not do is repeat a number inside the same year.

Do I need the HSN or SAC code on every invoice?

The code is a listed particular, and reporting requirements around it have changed over time depending on turnover and the nature of the supply. Confirm the current requirement for your turnover band with your CA rather than relying on a general article.

Is a proforma invoice a tax invoice?

No. A proforma is a quotation in invoice clothing. It does not carry the words "Tax Invoice", it does not create a tax liability, and your buyer cannot claim credit on it.