GST Invoice Format: What a Compliant Invoice Must Include (2026)

A GST tax invoice isn't just a bill you send to get paid — it's a legal document that determines whether your client can claim input tax credit. Get every required field right, and your invoice does its job for both of you. Miss one, and you've created a problem for your client's returns.

Why the format is legally fixed

Under the CGST Rules, 2017 (Rule 46), a registered supplier issuing a tax invoice must include specific fields. These aren't suggestions — they're statutory requirements. An invoice that omits mandatory information is not a valid tax invoice under GST law, which means the recipient cannot claim ITC against it.

This matters more than most people realise. A client who can't claim input credit on your invoice may push back on payment, ask for a revised invoice, or simply stop working with suppliers who get this wrong.

Mandatory fields checklist

1. Supplier details

   Your full legal name (as registered under GST), complete registered business address, and your GSTIN. These must exactly match your GST registration certificate.

2. Invoice number and date

   A consecutive, unique invoice serial number for the financial year — no gaps, no duplicates. The invoice date must also appear. See How to Number Your Invoices for a GST-compliant numbering approach.

3. Recipient details

   For a registered buyer: their name, address, and GSTIN. For an unregistered buyer: name, address, and state (with state code). The buyer's state determines whether you charge CGST+SGST or IGST.

4. Place of supply

   The state name and state code (two-digit code as per GST rules). This field is what formally determines the tax treatment — intra-state vs inter-state.

5. HSN or SAC code

   The Harmonised System of Nomenclature (HSN) code for goods, or the Services Accounting Code (SAC) for services. The number of digits required depends on your turnover. See HSN & SAC Codes Explained for how to find yours.

6. Description of goods or services

   A clear description of what you supplied — specific enough for the buyer and authorities to understand what was provided.

7. Quantity and unit (for goods)

   For goods, include quantity and the unit of measurement (kg, pieces, litres, etc.). For services, this field is not applicable.

8. Taxable value

   The value of the supply before tax. This is the base amount on which GST is calculated.

9. Applicable tax rate and amounts

   The GST rate (e.g., 18%), and the computed tax amounts broken out as either CGST + SGST (for intra-state) or IGST (for inter-state). Both the rate and the rupee amount must appear.

10. Total invoice value

    The total amount payable including GST — in both figures and words (words are required by rule).

11. Signature or digital signature

    The invoice must be signed — either physically or with a valid digital signature — by the supplier or an authorised representative.

12. Reverse charge statement (when applicable)

    If the transaction is subject to reverse charge mechanism (RCM), the invoice must explicitly state "Reverse Charge Applicable: Yes." This is mandatory — not optional — whenever a transaction is subject to reverse charge.

Optional but smart fields

These aren't legally required on every invoice but are good practice and often expected by clients:

• Your bank details — account number, IFSC, and bank name make it easy for clients to pay you directly.
• Payment terms — "Net 30" or "Due on receipt" sets clear expectations and reduces payment delays.
• PAN — useful when clients need it for TDS compliance (common for payments above ₹30,000 to professionals).
• Purchase Order (PO) number — larger clients often require their PO number on your invoice for internal approvals.

Common format mistakes

Wrong tax component: Charging CGST+SGST on an inter-state invoice (or IGST on an intra-state one) is a compliance error. The invoice must reflect the correct components based on place of supply.

Invoice serial number gaps: Deleting or skipping invoice numbers in a financial year creates a discrepancy that can attract scrutiny during GST audits. If you cancel an invoice, keep the cancelled record.

Incorrect GSTIN: A single transposed digit makes the entire invoice invalid for ITC purposes. Double-check every client GSTIN before saving it — the GST portal has a GSTIN verification lookup.

No taxable value shown separately: Some people just write the total amount with tax rolled in. GST rules require the taxable value (pre-tax) and the tax amount to appear as separate line items.

Amount in words missing: Rule 46 explicitly requires the total invoice value in words. It's easy to forget on a homemade template.

E-BillR's invoice form enforces every mandatory field — GSTIN, HSN/SAC, tax breakdown, place of supply, and amount in words — before an invoice can be saved. The new invoice guide walks through each field in the form. For a broader look at what makes an invoice professional beyond GST compliance, see How to Create a Professional Invoice.