If you run a GST-registered business in India, the tax invoice is the single most important document you issue. It is the legal proof of supply, the basis on which your buyer claims Input Tax Credit (ITC), and the record the GST department checks during any scrutiny. Get it wrong and your customer loses their credit - and you lose their trust. This guide walks through exactly how to make a GST invoice in 2026, field by field.
What is a GST invoice?
A GST invoice (or "tax invoice") is the bill a registered supplier issues to a buyer for the sale of goods or services. Under the CGST Rules, it must be raised before or at the time of removal of goods, or within 30 days of supplying a service. It is not just a receipt - it carries the tax breakup that lets your buyer claim ITC, so accuracy is non-negotiable.
Mandatory fields on a GST invoice
Rule 46 of the CGST Rules lists the fields every tax invoice must contain. Miss one and the invoice can be treated as defective:
- Supplier details - name, address and GSTIN of the seller.
- Invoice number - a consecutive serial, unique for the financial year (letters, numbers, "/" and "-" allowed, max 16 characters).
- Invoice date and, where relevant, the date of supply.
- Buyer details - name, address, and GSTIN if the buyer is registered.
- Place of supply and state code - this decides whether you charge IGST or CGST + SGST.
- HSN / SAC code for each item or service.
- Description, quantity, unit and taxable value of each item.
- Tax rate and tax amount - split into CGST, SGST/UTGST or IGST.
- Total invoice value in figures, and whether tax is on reverse charge.
- Signature or digital signature of the supplier.
HSN code requirements in 2026
The number of HSN digits depends on aggregate turnover in the previous financial year (Notification 78/2020-Central Tax, from 1 April 2021). Up to ₹5 crore, a 4-digit HSN code is mandatory on B2B tax invoices and optional on B2C invoices; above ₹5 crore, a 6-digit HSN code is mandatory on every tax invoice. Services use SAC codes on the same basis. A good billing tool keeps an HSN master so you never have to memorise codes - pick the product and the HSN code saved on it is filled in for you.
CGST + SGST or IGST? The one rule that trips everyone up
This is where most manual invoices go wrong. The split depends on the place of supply versus your location:
| Scenario | Tax to charge |
|---|---|
| Buyer in the same state (intra-state) | CGST + SGST (split equally) |
| Buyer in a different state (inter-state) | IGST (full rate) |
| Export / SEZ supply | Zero-rated (with LUT) or IGST + refund |
So an 18% item sold within Maharashtra is 9% CGST + 9% SGST, while the same item shipped to Gujarat carries 18% IGST. Mixing these up is the most common reason buyers reject an invoice. BizBharat Pro's GST Intelligence applies the correct split from your state and the customer's state every time.
How to make a GST invoice - step by step
Doing it manually in Excel works, but it is slow and error-prone. Here is the workflow, whether you use a spreadsheet or proper software:
- Add the buyer. Capture their name, GSTIN and state. With a saved party master you pick them from a list next time.
- Add line items. Select each product - its HSN code, rate and GST % are pulled from your catalogue.
- Let the tax calculate. The system applies CGST/SGST or IGST based on the place of supply and totals everything.
- Generate the invoice number. Use a continuous serial so there are no gaps - the department flags missing numbers.
- Share it. Download a PDF or send it straight to the customer on WhatsApp.
For businesses with turnover above ₹5 crore, e-invoicing (IRN + QR code generation from the government portal) is mandatory.
Common GST invoice mistakes to avoid
- Breaking the serial number sequence - every gap invites a query.
- Wrong place of supply - leads to the wrong CGST/SGST/IGST split.
- Missing HSN codes - blocks your buyer's ITC.
- Issuing a "bill of supply" with tax - composition dealers and exempt suppliers must use a bill of supply, not a tax invoice.
- Rounding errors - the tax amount must match the rate exactly.
Make GST invoices in under a minute
Manually checking every field is exhausting when you raise dozens of bills a week. With BizBharat Pro you pick the customer, add products, and a clean, compliant GST invoice - the HSN codes saved on your products, the right tax split, a continuous serial number and a professional PDF - is ready in seconds. It runs in the browser on your phone or computer, so you can bill from anywhere with an internet connection.
GST compliance does not have to be painful. Get the fields right, automate the tax maths, and keep your numbering clean - and your invoices will sail through any scrutiny.