---
title: "GST Invoice Format 2026: Mandatory Fields, Rules, and Free Templates"
description: "Every GST invoice must include 16 mandatory fields. Missing even one can block your customer's input tax credit. Here is the complete format with rules, examples, and free templates."
author: "Amresh Kumar"
published: 2026-03-23T14:14:53.000Z
updated: 2026-09-06T09:50:57.961Z
url: https://blog.mybillplease.com/gst-invoice-format-guide
---
# GST Invoice Format 2026: Mandatory Fields, Rules, and Free Templates

## Key takeaways

- Rule 46 requires 16 mandatory fields on every tax invoice; missing one blocks the customer's ITC and attracts Rs 50 per invoice.
- Invoice numbers must be sequential, up to 16 characters, using only letters, digits, dash and slash; never reuse or amend one.
- HSN codes need 4 digits up to Rs 5 crore turnover, 6 above, and 8 for exports and imports.
- B2B invoices must carry the customer GSTIN and place of supply; B2C invoices need place of supply only for inter-state sales above Rs 2.5 lakh.

## Why GST Invoice Format Matters

A GST invoice is not just a bill — it is a legal document that determines input tax credit for your customer. If your invoice is missing mandatory fields or has wrong information, your customer cannot claim ITC on that purchase. This costs them real money and strains business relationships.

Under Section 31 of the CGST Act, every registered person making a taxable supply must issue a tax invoice. The format and content requirements are specified in Rule 46 of the CGST Rules. These rules apply to every business — whether you sell products, provide services, or do both.

After the GST 2.0 reform in September 2025, the invoice format itself has not changed. But the tax rates on your invoices have — the 12% and 28% slabs no longer exist, replaced by 5%, 18%, and the new 40% luxury slab. Make sure your invoicing software reflects the [new GST rates](/new-gst-rates-2026).

This guide covers every mandatory field, common format mistakes, B2B vs B2C invoice differences, and how to create compliant invoices quickly. Use our [free invoice generator](https://www.mybillplease.com/tools/invoice-generator) to create a GST-compliant invoice right now, or browse [invoice format templates](https://www.mybillplease.com/tools/invoice-format) for different industries.

## 16 Mandatory Fields in a GST Invoice
Every tax invoice must include all of these — as per Rule 46 of CGST Rules
- Supplier name, address, and GSTIN (your business details)
- Invoice number — unique, sequential, up to 16 characters, no special characters except dash and slash
- Invoice date — date of issue, not the date of supply (unless different)
- Recipient name (customer or buyer name)
- Recipient GSTIN (for B2B invoices — mandatory if the buyer is GST-registered)
- Recipient address and state code (determines IGST vs CGST+SGST)
- HSN code or SAC code for each item or service (4 or 6 digits based on turnover)
- Description of goods or services — clear enough to identify the product
- Quantity and unit of measurement (for goods)
- Total value of supply (before tax)
- Taxable value after discounts
- GST rate applied to each item (5%, 18%, or 40% under GST 2.0)
- Tax amount split: CGST + SGST (intra-state) or IGST (inter-state)
- Place of supply — state where goods are delivered or services consumed
- Whether tax is payable on reverse charge basis (if applicable)
- Signature or digital signature of the supplier (or authorised representative)

## B2B Invoice vs B2C Invoice: Key Differences
The format changes based on whether your customer is GST-registered
| B2B Invoice | B2C Invoice |
| --- | --- |
| Customer GSTIN | Mandatory | Not required |
| Place of Supply | Mandatory | Mandatory only for inter-state > Rs 2.5L |
| HSN Code | 4 or 6 digits required | 4 or 6 digits required |
| Tax Breakup | CGST+SGST or IGST line-wise | CGST+SGST or IGST (can be consolidated) |
| Invoice Serial | Unique, sequential | Unique, sequential |
| Reported in GSTR-1 | Table 4 — invoice-wise | Table 5 (Large) or Table 7 (Small) |
| ITC for customer | Customer can claim ITC | No ITC — consumer is end user |
| E-invoice | Required if turnover > Rs 5 crore | Not required |

## GST Invoice Number Rules

The invoice number is one of the most commonly botched fields. Here are the rules from Rule 46 of CGST Rules:

**Sequential:** Invoice numbers must be in a consecutive serial order. You cannot skip numbers or reuse them. If you issue invoice MBP-001, the next must be MBP-002, not MBP-005.

**Maximum 16 characters:** The invoice number cannot exceed 16 characters including any prefix. Characters allowed are alphanumeric, dash (-), and forward slash (/) only. No spaces, dots, or other special characters.

**Financial year reset:** You can reset the series at the start of each financial year. Common format: MBP/2026-27/001 for FY 2026-27. Make sure the total stays within 16 characters.

**Multiple series:** A business can maintain multiple invoice series — for example, one for sales (INV-001) and one for exports (EXP-001). Each series must be independently sequential.

**No amendments to invoice number:** Once issued, an invoice number cannot be changed. If there is an error, issue a credit note and create a new invoice with the next available number.

In [myBillPlease](https://www.mybillplease.com/signup), invoice numbers auto-increment following your configured series. You set the prefix and starting number once — the system handles sequential numbering automatically.

## HSN Code Requirements on GST Invoices

HSN codes are mandatory on every GST invoice. The number of digits required depends on your annual turnover:

**Turnover up to Rs 5 crore:** 4-digit HSN code required on invoices. Example: 6109 for T-shirts.

**Turnover above Rs 5 crore:** 6-digit HSN code required. Example: 610910 for T-shirts of cotton.

**Exports and imports:** 8-digit HSN code required. Example: 61091010 for T-shirts of cotton, knitted.

> **Penalty for wrong or missing HSN codes**
> 
> Using the wrong HSN code or omitting it attracts a penalty of Rs 50 per invoice under Section 125 of the CGST Act, up to a maximum of Rs 25,000 per financial year. This adds up fast if you issue hundreds of invoices per month.

Find the correct HSN code for any product using our [HSN code directory](https://www.mybillplease.com/hsn) — all 97 chapters with 22,000+ codes searchable by name or number. Or use the [HSN code finder tool](https://www.mybillplease.com/tools/hsn-code) for quick lookups.

## Common GST Invoice Format Mistakes
- **Missing Customer GSTIN** — For B2B invoices, customer GSTIN is mandatory. Without it, the invoice is treated as B2C and your customer cannot claim ITC. Always collect and verify GSTIN before invoicing.
- **Wrong State Code** — The state code determines IGST vs CGST+SGST split. Wrong state code means wrong tax calculation. State code comes from the first 2 digits of GSTIN — verify it matches the delivery address.
- **Tax Not Shown Separately** — GST must be shown as a separate line — CGST and SGST for intra-state, or IGST for inter-state. Showing a lump-sum amount without tax breakup makes the invoice non-compliant.
- **Invoice Date Issues** — Invoice date should be the date of issue. For goods, it must be issued before or at the time of removal. For services, within 30 days of supply completion. Backdating invoices is illegal.
- **Exceeding 16-Character Number** — Invoice numbers longer than 16 characters or containing invalid characters get rejected on the GST portal. Keep your prefix short and let the system handle numbering.
- **Missing Place of Supply** — Place of Supply is mandatory for all B2B invoices and for inter-state B2C invoices above Rs 2.5 lakh. Missing it causes classification errors in GSTR-1 filing.

> **Create GST-Compliant Invoices in 30 Seconds**
> 
> You have two options for creating proper GST invoices:
> 
> **Option 1: Use our free invoice generator.** Visit [mybillplease.com/tools/invoice-generator](https://www.mybillplease.com/tools/invoice-generator), fill in your details, add items with HSN codes, and download a professional PDF invoice. No signup required. Works for one-off invoices or when you need a quick bill.
> 
> **Option 2: Use myBillPlease for ongoing billing.** [Sign up free](https://www.mybillplease.com/signup), add your products with HSN codes and GST rates once, and create invoices in 30 seconds every time. Customer details auto-fill, tax calculates automatically, invoice numbers auto-increment, and your GSTR-1 report generates from all your invoices at month-end. Choose from 7 professional PDF templates.
> 
> Both options ensure your invoices include all 16 mandatory fields. The free plan has no invoice limit and no expiry — use it as long as you need.

_[form: gst-invoice-format-en]_

**Create Perfect GST Invoices — Free**
All 16 mandatory fields included automatically. 7 professional templates. Auto-calculated tax. No credit card needed.

[Get Started Free](/signup)

## FAQ

### What are the mandatory fields in a GST invoice?

A GST invoice must include 16 mandatory fields as per Rule 46 of CGST Rules: supplier name, address, and GSTIN; unique sequential invoice number (max 16 characters); invoice date; recipient name and address; recipient GSTIN (for B2B); recipient state code; HSN or SAC code for each item; description of goods or services; quantity and unit; total value before tax; taxable value after discounts; applicable GST rate; tax amount split as CGST plus SGST or IGST; place of supply; reverse charge indicator if applicable; and supplier signature. Missing any of these fields can result in the invoice being treated as non-compliant, which blocks your customer from claiming input tax credit on that purchase.

### What is the correct GST invoice number format?

GST invoice numbers must be consecutive and sequential with no gaps. The maximum length is 16 characters. Only alphanumeric characters, dashes, and forward slashes are allowed — no spaces, dots, or other special characters. A common format is PREFIX/YEAR/NUMBER, for example MBP/26-27/0001 for the first invoice of FY 2026-27. You can maintain multiple series for different document types. Once issued, an invoice number cannot be changed or reused. If you find an error, issue a credit note against the original invoice and create a new one with the next number in the series.

### How many digits of HSN code are required on a GST invoice?

The number of HSN code digits required depends on your annual aggregate turnover. Businesses with turnover up to Rs 5 crore must use 4-digit HSN codes on their invoices. Businesses with turnover above Rs 5 crore must use 6-digit codes. For exports and imports, 8-digit HSN codes are mandatory regardless of turnover. Using the wrong number of digits or omitting HSN codes entirely attracts a penalty of Rs 50 per invoice under Section 125 of the CGST Act, capped at Rs 25,000 per financial year. Use the free HSN code directory at mybillplease.com/hsn to find the correct code for any product.

### What is the difference between a tax invoice and a bill of supply?

A tax invoice is issued when you make a taxable supply — it includes GST amount and allows the customer to claim input tax credit. A bill of supply is issued when you make an exempt supply or when you are registered under the composition scheme. The bill of supply does not include GST amount because no tax is charged. The format is similar but a bill of supply explicitly states that tax is not charged and the customer cannot claim ITC. If you are a regular GST taxpayer selling taxable goods or services, you issue a tax invoice. If you sell exempt goods like fresh vegetables or unbranded food grains, you issue a bill of supply.

### Can I create a GST invoice in Excel?

Yes, you can create GST invoices in Excel, but it is risky for compliance. Excel does not automatically validate HSN codes, calculate tax correctly based on place of supply, or maintain sequential invoice numbers. Common errors include wrong CGST vs IGST calculation, missing mandatory fields, and broken number sequences. A rising search query is gst bill format in excel with formula — this shows many businesses still use Excel. While it works for very small volumes of 5 to 10 invoices per month, any larger volume benefits from proper billing software. myBillPlease is free, handles all GST calculations automatically, and generates GSTR-1 ready reports from your invoices.

### Is digital signature mandatory on GST invoices?

A signature or digital signature of the supplier or their authorised representative is listed as a mandatory field in Rule 46 of the CGST Rules. However, in practice, the GST department has been lenient about this requirement for digitally generated invoices. Most billing software including myBillPlease generates invoices as PDF documents that are considered valid even without a wet signature, provided they contain all other mandatory fields and are generated from an authenticated system. For e-invoices generated through the IRP portal, the digital signature is embedded in the QR code and IRN, so no additional signature is needed.

### What happens if my GST invoice format is wrong?

If your GST invoice is missing mandatory fields or has incorrect information, several consequences follow. First, your customer cannot claim input tax credit on that invoice — this directly costs them money equal to the tax amount. Second, the invoice may not be accepted during GSTR-2B reconciliation, creating a mismatch that triggers audit queries. Third, repeated format violations can attract a penalty of Rs 50 per invoice under Section 125 of CGST Act, up to Rs 25,000 per year. Fourth, incorrect invoices affect your GSTR-1 filing accuracy, which can lead to GST notices. The simplest way to avoid all these issues is to use billing software that enforces the correct format automatically.