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GST billing guide

GST invoice format: mandatory fields and rules

Short answer

A GST tax invoice must show the supplier’s and recipient’s name, address and GSTIN, a unique consecutive invoice number (up to 16 characters) and date, the HSN/SAC code, item description, quantity, taxable value, the GST rate and amount split into CGST/SGST or IGST, the place of supply, and the supplier’s signature or digital signature.

Updated 2026-06-03 · 399Apps · General GST information, not tax advice

How to make a GST-compliant invoice: step by step

Whether you use software or a template, a valid GST invoice needs the same fields in the same logical order.

  1. 1

    Add your business details and GSTIN

    Put your trade name, address and GSTIN at the top, with the title "Tax Invoice".

  2. 2

    Assign a unique invoice number and date

    Use a consecutive serial number (maximum 16 characters, letters/numbers/hyphen/slash) unique for the financial year, plus the invoice date.

  3. 3

    Enter the customer details and place of supply

    Add the recipient’s name, address, GSTIN (if registered) and the place of supply — this decides whether you charge CGST+SGST or IGST.

  4. 4

    List the items with HSN/SAC

    For each line add the description, HSN/SAC code, quantity, unit, rate and taxable value (after any discount).

  5. 5

    Apply the correct GST

    Charge CGST + SGST for intra-state supplies or IGST for inter-state supplies, showing the rate and amount for each tax head.

  6. 6

    Show totals, reverse charge and signature

    Add the total taxable value, total tax, invoice total (in figures and words), whether tax is payable on reverse charge, and the authorised signature or digital signature.

What is a GST invoice?

A GST invoice (tax invoice) is the document a registered supplier must issue for a taxable supply of goods or services. It records what was sold, to whom, at what value, and how much GST applies — and it is the basis on which the buyer claims input tax credit. The mandatory contents are set out in Rule 46 of the CGST Rules.

Mandatory fields in a GST invoice (Rule 46)

A compliant tax invoice must contain:

  • • Supplier’s name, address and GSTIN.
  • • A consecutive invoice number, unique for the financial year (up to 16 characters).
  • • Date of issue.
  • • Recipient’s name, address and GSTIN (or state and place of supply if unregistered and value above ₹50,000).
  • • HSN code for goods or SAC for services.
  • • Description, quantity/unit, and total value of goods or services.
  • • Taxable value after discount, the GST rate, and the tax amount split into CGST, SGST/UTGST or IGST (and cess if any).
  • • Place of supply and the state code for inter-state sales.
  • • Whether GST is payable on reverse charge.
  • • Signature or digital signature of the supplier or authorised person.

Tax invoice vs bill of supply

A tax invoice is issued when GST is charged on a taxable supply. A bill of supply is issued instead when no GST is charged — for example by a composition dealer or for exempt/nil-rated goods — and it omits the tax break-up. Charging GST on a bill of supply, or issuing a bill of supply where a tax invoice is required, is a compliance error.

Time limits to issue a GST invoice

For goods, the invoice must be issued on or before the removal or delivery of the goods. For services, it must be issued within 30 days of supplying the service (45 days for banks, insurers and financial institutions). Issuing invoices late or out of sequence can create GST and reconciliation problems.

Invoice numbering rules

Invoice numbers must be consecutive, unique for the financial year, and no longer than 16 characters using only letters, numbers, hyphen and slash. You may run multiple series (for example per branch or per type), but each must be unique and unbroken — gaps or duplicates raise questions during scrutiny.

How 399Apps helps

Nidhi Books (by 399Apps) generates GST-compliant tax invoices automatically — correct invoice numbering, HSN/SAC, place-of-supply-based CGST/SGST or IGST, a UPI QR on the PDF, and e-invoice/IRN where required — so every bill meets Rule 46 without manual checking.

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FAQ

GST invoice format — frequently asked questions

What are the mandatory fields in a GST invoice? +
A GST invoice must show the supplier and recipient name, address and GSTIN, a unique consecutive invoice number and date, HSN/SAC, item description and quantity, taxable value, GST rate and amount (CGST/SGST or IGST), place of supply, and the supplier’s signature.
What is the maximum length of a GST invoice number? +
A GST invoice number can be up to 16 characters, using letters, numbers, hyphen (-) and slash (/). It must be consecutive and unique for the financial year; you may run multiple series as long as each is unbroken.
What is the difference between a tax invoice and a bill of supply? +
A tax invoice is issued when GST is charged on a taxable supply and shows the tax break-up. A bill of supply is issued when no GST is charged — by composition dealers or for exempt supplies — and omits the tax amount.
What is the time limit to issue a GST invoice? +
For goods, the invoice must be issued on or before removal or delivery. For services, it must be issued within 30 days of supply (45 days for banks, NBFCs and insurers).
Is a signature mandatory on a GST invoice? +
Yes. A GST invoice must carry the physical or digital signature of the supplier or an authorised person. A digital signature or a valid e-invoice QR/IRN satisfies this requirement for electronically issued invoices.

Related

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