How to make a GST invoice: every mandatory field under Rule 46 explained

A valid GST invoice is a tax invoice that carries every field listed in Rule 46 of the CGST Rules, 2017: your GSTIN, a unique serial number, the date, your buyer's details, HSN or SAC codes, taxable value, the tax split into CGST and SGST (or IGST) and a signature. Miss a field and your buyer may lose input tax credit, and you may face a penalty. This guide walks through every field with a worked example.

Why the invoice format matters more than it looks

Under GST the invoice is not just a bill. It is the document that lets your buyer claim input tax credit (ITC), the document that feeds your GSTR-1, and the document an officer will ask for during a road check or an audit. Section 31 of the CGST Act makes it compulsory for every registered person supplying taxable goods or services to issue a tax invoice, and Rule 46 sets out exactly what it must contain.

Because the buyer's ITC depends on your invoice matching what you report in GSTR-1 (and what then appears in their GSTR-2B), a small typo in a GSTIN or a wrong tax split is not a cosmetic problem. It becomes a phone call from your customer's accountant asking you to fix it, or worse, a customer who quietly stops buying from you because your paperwork keeps failing their reconciliation.

Every mandatory field under Rule 46

Here is the complete list, in the order it appears in the rule, with what each one means in practice.

(a) Your name, address and GSTIN. Use the legal name and principal place of business exactly as on your registration certificate. If you invoice from a branch in another state, use that branch's GSTIN.

(b) A consecutive serial number, unique for the financial year. Up to 16 characters, using letters, numbers, hyphens and slashes only. Something like INV/26-27/0042 works. Numbering has its own set of traps, covered in invoice numbering rules.

(c) Date of issue. The date the invoice is raised, which for goods should be on or before the date of dispatch.

(d) Recipient's name, address and GSTIN if they are registered. This is the field that most often breaks ITC. Verify the GSTIN before you save a customer, not after.

(e) and (f) Recipient's details when unregistered. If the buyer is unregistered and the invoice value is ₹50,000 or more, you must record their name, address, delivery address, and the state name and code. Below ₹50,000 you need these only if the buyer asks.

(g) HSN code for goods or SAC for services. Four digits if your aggregate turnover in the previous year was up to ₹5 crore (optional on B2C invoices at that level), six digits above ₹5 crore, and eight digits on export invoices. See HSN and SAC codes explained.

(h) Description of goods or services. Enough for a stranger to understand what was sold.

(i) Quantity and unit for goods, such as 12 PCS or 250 MTR. Use the unit quantity codes from the GST portal.

(j) Total value of the supply before adjustments.

(k) Taxable value after any discount or abatement. Discounts shown on the invoice are deducted before tax is calculated.

(l) Rate of tax (CGST, SGST or UTGST, IGST, and cess if any) for each line.

(m) Amount of tax charged for each of those components. Show CGST and SGST as separate amounts, not one combined "GST" figure.

(n) Place of supply with the state name for inter-state supplies. This is what decides whether IGST or CGST plus SGST applies, explained in CGST, SGST and IGST and place of supply.

(o) Address of delivery where it differs from the place of supply, for example a bill-to, ship-to sale.

(p) Whether tax is payable on reverse charge. A simple "Reverse charge: No" line on every invoice keeps this covered.

(q) Signature or digital signature of the supplier or an authorised person. This is not required when the invoice is issued electronically in line with the Information Technology Act, which is why a PDF generated by an invoicing tool does not need a scanned signature.

(r) QR code with IRN when e-invoicing applies to you. That is a separate topic, covered in e-invoicing explained.

Rule 46 also requires exporters to print the words "Supply meant for export on payment of integrated tax" or "Supply meant for export under bond or letter of undertaking without payment of integrated tax" along with the country of destination.

B2B versus B2C: what changes on the invoice

The rule is the same for both, but the practical requirements differ because of what the buyer will do with the document.

The ₹200 relaxation under Section 31(3)(b) is what allows a shop to print a simple bill for a ₹150 sale. It applies only when the buyer is unregistered and does not ask for a tax invoice; the sales still have to be totalled in a consolidated invoice for the day.

Original, duplicate, triplicate: the copies rule

Rule 48 says an invoice for goods must be prepared in triplicate:

• Original for recipient, which the buyer keeps for their ITC claim.
• Duplicate for transporter, which travels with the goods and is shown at any check.
• Triplicate for supplier, your own record.

For services, two copies: original for recipient and duplicate for supplier. Each copy should be marked with those words. When you generate a PDF and share it, the same file serves all purposes, but if the goods are physically moving, keep a printed transporter copy in the vehicle (or an e-way bill, which is covered in the e-way bill guide).

When you must issue the invoice

Section 31 and Rule 47 set the time limits, and these limits also fix when the tax becomes payable.

For goods, "at removal" means the invoice has to exist before the truck leaves. A delivery challan can accompany goods in some situations, but not for a plain sale. For services, note that the 30-day window is a maximum: the time of supply (and therefore the month in which GST is due) is the earlier of the invoice date and the payment date, so if a client pays you an advance, the tax is due on that advance even before you invoice.

A worked example: Kochi electronics shop, intra-state B2B sale

Suppose Marine Drive Electronics in Kochi, Kerala (GSTIN starting with 32) sells a laptop to a registered Kochi architecture firm on 5 June 2026. Laptops are taxed at 18%. Because both parties are in Kerala, the tax splits into CGST and SGST.

The arithmetic: ₹61,750 × 9% = ₹5,557.50 for each of CGST and SGST, total tax ₹11,115, so ₹61,750 + ₹11,115 = ₹72,865. Round the final amount to the nearest rupee under Section 170 if your invoice policy is to round; ₹72,865 is already whole here.

Had the buyer been in Coimbatore, Tamil Nadu, the same taxable value would carry IGST at 18%, which is ₹11,115 in one line, and the invoice would show "Place of supply: Tamil Nadu (33)". The buyer pays the same amount either way; what changes is which government gets the tax and which column of GSTR-1 you fill.

The invoice must show: the shop's name, address and GSTIN; serial number INV/26-27/0087; date 05-06-2026; the architecture firm's name, address and GSTIN; HSN 8471 and description; quantity 1 NOS; the taxable value, rate and both tax amounts; place of supply Kerala; "Reverse charge: No"; and the copy marking. That is a complete Rule 46 invoice.

Optional fields that are worth adding

Nothing stops you adding more than the law demands, and a few extras save arguments later.

• Payment terms and due date. "Payment due within 15 days" sets up your right to interest under the MSMED Act if you are a registered MSME (see the 45-day rule).
• Bank details and a UPI QR code. The buyer pays faster when the invoice tells them how.
• Your PAN and Udyam number. Buyers subject to Section 43B(h) want your Udyam number on file.
• A "subject to Kochi jurisdiction" line if you sell across states.
• Amount in words, which many buyers' accounts teams still insist on.

Common mistakes that get your customer's ITC blocked

Section 16(2)(a) allows ITC only when the recipient holds a valid tax invoice, and Rule 36(2) says the document must at minimum carry the tax amount, description, total value, both GSTINs and the place of supply. These are the errors that cause trouble most often.

1. Wrong or old GSTIN of the buyer. The invoice lands in someone else's GSTR-2B, or nowhere at all. Check the GSTIN and the legal name against the portal before saving the customer.
2. Charging CGST and SGST on an inter-state sale (or IGST on an intra-state one). The buyer cannot claim credit of the wrong tax type, and you have to issue a credit note and a fresh invoice.
3. Combined "GST 18%" line instead of CGST 9% and SGST 9%. Rule 46 wants each component shown separately.
4. Missing HSN. The GSTR-1 HSN summary (Table 12) is now validated line by line; invoices without HSN codes cause filing errors for you and mismatches for the buyer.
5. Duplicate or reused invoice numbers. GSTR-1 rejects duplicates and, if you are under e-invoicing, the IRP rejects them outright.
6. Invoice date earlier than the GST registration date. Only a revised invoice under Rule 53 can cover that period.
7. Discounts given after the sale but not shown on the invoice. A post-sale discount does not reduce taxable value unless it meets Section 15(3)(b), so plan discounts before invoicing where you can, or handle them by credit note as explained in the credit note and debit note guide.
8. Forgetting the "composition taxable person" line if you are on the composition scheme, or issuing a tax invoice when you should issue a bill of supply. The differences are covered in tax invoice vs bill of supply vs proforma.
9. Not filing GSTR-1 on time. Even a perfect invoice does not help the buyer until you report it. Late filing is the single biggest reason ITC "disappears" from a buyer's GSTR-2B.

Under Section 122(1) issuing an incorrect invoice, or supplying goods without one, attracts a penalty of ₹10,000 or the tax involved, whichever is higher. Confirm the current penalty provisions with your CA, as they are updated from time to time.

How VyaparKit helps

The GST invoice tool lays out every Rule 46 field, numbers invoices in a financial-year series, and splits the tax into CGST and SGST or IGST automatically from the place of supply. You can check a buyer's GSTIN with the free GSTIN checker before saving them, look up the right code with HSN and SAC lookup, and verify a tax split with the CGST, SGST and IGST calculator. Invoices export to PDF, carry a Pay-via-UPI button on the share link, and feed a GST report in GSTR-1 order. VyaparKit does not generate e-invoice IRNs or file returns; if e-invoicing applies to you, you still need an IRP.

Next steps

• Compare your current invoice format line by line against the Rule 46 list above and add whatever is missing.
• Verify the GSTIN of every regular customer once and save it, so you never retype it.
• Decide your invoice series for FY 2026-27 and stick to it for the whole year.
• Set a calendar reminder for the 11th of every month so invoices reach your buyers' GSTR-2B on time.
• If your turnover has crossed ₹5 crore, read the e-invoicing guide before your next B2B sale.