GST Invoice Format (2026): Mandatory Fields, Sample Bill and Free Template

Most "GST invoice format" pages give you a template to download and stop there. The template is the easy part. The hard part is knowing which fields the law actually requires, which ones change depending on who the buyer is, and which small mistakes make your customer lose their input tax credit.

This guide goes through the GST invoice format the way the law sets it out: field by field from Rule 46 of the CGST Rules, 2017, with a filled-in sample bill, the e-invoice and HSN rules that apply in 2026, and the checks to run before a bill leaves your counter. It is written for shop owners, wholesalers and service providers who issue their own bills, not for tax professionals, so every rule comes with a plain example.

Quick answer: what a GST invoice must contain

A GST tax invoice must show, at minimum:

• Your business name, address and GSTIN
• A unique invoice number of up to 16 characters, and the date
• The buyer's name, address and GSTIN if they are registered
• For each line: description, HSN or SAC code, quantity and unit
• The taxable value after any discount
• The GST rate and amount, split into CGST + SGST (same state) or IGST (different state)
• The place of supply, with the state name, for inter-state sales
• Whether reverse charge applies
• Your signature or digital signature

Everything else on the page, such as your logo, bank details and a UPI QR code, is optional, but useful.

The GST invoice format, field by field (Rule 46)

Rule 46 of the CGST Rules lists the particulars a tax invoice must contain. Here they are in the order the rule gives them, with what each one means in practice.

Two provisos in Rule 46 matter to small shops. First, an electronic invoice does not need a physical signature. Second, for small sales to unregistered customers who do not ask for an invoice, you may issue one consolidated tax invoice at the close of each day covering all of them, instead of one bill per sale. Most shops still issue individual bills because customers want them, but the option exists.

A sample GST invoice, filled in

Here is what a correct intra-state tax invoice looks like for a hardware shop in Tamil Nadu selling to a registered contractor in the same state. The values are illustrative.

TAX INVOICE                                   ORIGINAL FOR RECIPIENT

Sri Murugan Hardware                  Invoice no:   SMH/25-26/0418
12, Raja Street, Coimbatore 641001    Date:         17-10-2026
GSTIN: 33ABCDE1234F1Z5                Place of supply: Tamil Nadu (33)
                                      Reverse charge:  No
Bill to:
Kumar Constructions
45, Avinashi Road, Coimbatore 641018
GSTIN: 33PQRSX5678K1Z2

#  Description          HSN    Qty   Unit  Rate     Taxable   GST
1  PVC pipe 1 inch      3917   40    NOS   180.00   7,200.00  18%
2  LED bulb 9W          8539   25    NOS   90.00    2,250.00  18%
3  Cement OPC 53        2523   10    BAG   380.00   3,800.00  18%
                                     Less discount  (250.00)
                                     Taxable value  13,000.00
                                     CGST @ 9%       1,170.00
                                     SGST @ 9%       1,170.00
                                     Invoice total  15,340.00

Amount in words: Fifteen thousand three hundred and forty rupees only
For Sri Murugan Hardware            Authorised signatory

If the same order went to a contractor in Bengaluru instead, three things change: the place of supply becomes Karnataka (29), the tax lines become a single IGST @ 18% = ₹2,340.00, and the invoice total stays the same. The rate does not change between states; only the split does. Our guide to CGST, SGST and IGST walks through more examples of that split.

Note the discount line. Rule 46(k) asks for the taxable value after discount, and GST is charged on that reduced amount. A bill that discounts the total after adding tax overcharges your customer and overstates your output tax.

Invoice numbering rules

Rule 46(b) is stricter than most people expect. Your invoice number must be:

• Consecutive within a series
• Unique for the financial year (1 April to 31 March)
• No longer than 16 characters
• Made of letters, numbers, and only two special characters: hyphen ( - ) and slash ( / )

You may run more than one series. Many businesses keep one per branch, counter or type of document, for example SMH/25-26/0418 for tax invoices and SMH/BOS/0032 for bills of supply. What you cannot do is reuse a number in the same financial year, or skip numbers without a record of why (a cancelled bill should be kept and marked cancelled, not deleted).

Changing billing software mid-year is the most common way to break this rule. If your new app starts again at "INV-1", you may duplicate a number you already issued. Set a fresh prefix in the new app (for example BZ-) so its series can never collide with the old one.

How many copies, and when to issue the bill

Copies (Rule 48). For goods, prepare the invoice in triplicate: the original marked ORIGINAL FOR RECIPIENT, the duplicate marked DUPLICATE FOR TRANSPORTER, and the triplicate marked TRIPLICATE FOR SUPPLIER. For services, two copies are enough: original for the recipient and duplicate for the supplier. If you issue a PDF and keep the record in your billing software, you still need to be able to produce each copy when asked.

Timing (Section 31 and Rule 47). For goods, the invoice is issued before or at the time the goods are removed for supply, or delivered. For services, it must be issued within 30 days of the date the service is supplied. Issuing the bill weeks later is not a formality problem; it can shift the tax into the wrong return period.

Tax invoice, bill of supply or something else?

Not every bill a GST-registered business issues is a "tax invoice". Using the wrong document is a frequent and avoidable error.

If you are under the composition scheme, you cannot issue a tax invoice or collect GST from your customer. Your document is a bill of supply, and it should say "composition taxable person, not eligible to collect tax on supplies".

E-invoicing: does it apply to you in 2026?

E-invoicing is not a different invoice format. It is your normal tax invoice, reported to the government's Invoice Registration Portal, which returns an Invoice Reference Number (IRN) and a signed QR code that you print on the bill (Rule 46(r)).

• Who must e-invoice: businesses whose aggregate annual turnover has exceeded ₹5 crore in any financial year from 2017-18 onwards. This threshold has applied since 1 August 2023.
• Which bills: B2B invoices, exports, and credit and debit notes. B2C sales do not need an IRN.
• Time limit: since 1 April 2025, businesses with turnover of ₹10 crore or more cannot report an e-invoice that is more than 30 days old (GSTN advisory).
• Below ₹5 crore: e-invoicing is optional, and most small shops do not need it.

If your turnover crosses ₹5 crore, you will need a billing tool that connects to the IRP. That is a real reason to choose a paid billing product, and we cover which apps support it in our comparison of the best GST billing apps.

HSN digits and GST rates on the invoice

HSN digits. Notification 78/2020 sets how many digits of the HSN (goods) or SAC (services) code you must print:

Printing more digits than required is always fine. Many businesses print the full 8-digit code from the customs tariff because it removes any doubt about the rate.

Rates. From 22 September 2025, GST moved to a simpler structure: most goods and services are taxed at 5% or 18%, a 40% rate applies to luxury and sin goods, and essentials are at 0%. A few special rates continue, such as 3% on gold. The old 12% and 28% slabs were removed for most items, so invoices still printed with 12% or 28% on everyday goods are a warning sign that your item master was never updated. Check each item's current rate with your CA or the CBIC rate notifications before you bill it.

Which format should you use: template or app?

A GST invoice can be made in Excel, in Word, in a free online generator or in a billing app. All of them can produce a compliant bill. They differ in how easy they make it to stay compliant on bill number 4,000.

Templates fail in predictable ways: someone copies last month's file and forgets to change the number, or overwrites the IGST formula with CGST. A billing app removes those two failure points because the number and the tax split are worked out for you.

Making a GST invoice in BillZap

BillZap is our free GST billing app for Android, and it produces the format above without a template. You enter your shop name, GSTIN and UPI ID once. After that each bill takes about 30 seconds:

1. Pick a saved customer, or type a new one with their GSTIN and state.
2. Add items by tapping or by speaking in any of 12 Indian languages. The HSN code and rate come from your saved catalogue.
3. BillZap chooses CGST + SGST or IGST from the place of supply and shows you which before you save.
4. Save, then share the PDF on WhatsApp or print it. Unpaid bills carry a UPI QR code for your own UPI ID.

The invoice numbering follows Rule 46: one prefix you set, consecutive numbers, unique for the year. Each month's sales roll into a GST summary laid out for GSTR-1, which you can export as PDF or CSV for your accountant. BillZap works fully offline and needs no account. It does not generate e-invoices or e-way bills, so it suits businesses below the ₹5 crore e-invoice threshold.

Checklist before a GST invoice leaves your counter

Run through these before you hand over or send the bill:

• Your GSTIN and the buyer's GSTIN are both correct (15 characters each, state code first)
• The invoice number is new, under 16 characters, and follows your series
• Every line has an HSN or SAC code with enough digits
• Discounts are applied before tax
• The tax split matches the place of supply: CGST + SGST within the state, IGST across states
• The place of supply is printed for inter-state sales
• Reverse charge is marked yes or no
• Large cash sales of ₹50,000 or more carry the buyer's name, address and state
• The totals add up and the amount in words matches the figure
• The bill is signed, or issued electronically

FAQ: GST invoice format

What is the format of a GST invoice?

A GST invoice has no single prescribed layout, but it must contain the particulars in Rule 46 of the CGST Rules: supplier name, address and GSTIN; a unique invoice number and date; buyer details; HSN or SAC code, description, quantity and taxable value for each item; the tax rate and amount split into CGST and SGST or IGST; place of supply; reverse charge status; and a signature.

Is HSN code mandatory on a GST invoice?

Yes, for most businesses. If your turnover was up to ₹5 crore, you must print at least 4 digits of the HSN code on B2B invoices; on B2C invoices it is optional. Above ₹5 crore, at least 6 digits are mandatory on all invoices.

Can I make a GST invoice without the buyer's GSTIN?

Yes. If the buyer is not registered, you issue a tax invoice without their GSTIN. If the taxable value is ₹50,000 or more, you must still record their name, address, delivery address and state. Below ₹50,000, you record these only if the buyer asks.

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

A tax invoice charges GST and lets a registered buyer claim input tax credit. A bill of supply charges no GST and is used for exempt goods or services, or for any sale by a composition dealer.

Do I need to put a QR code on my GST invoice?

Only the e-invoice QR code (with the IRN) is a legal requirement, and only for businesses that must e-invoice, currently those with turnover above ₹5 crore, on B2B bills. A UPI payment QR code is optional, but it helps you get paid on the spot.

Can I issue a GST invoice from my mobile phone?

Yes. A GST invoice can be issued electronically, and an electronic invoice does not need a physical signature. A billing app on your phone can produce a compliant invoice and share it as a PDF.

The bottom line

The GST invoice format is not a design; it is a checklist. Get the Rule 46 fields right (GSTINs, a clean number series, HSN codes, tax after discount, and the correct CGST + SGST or IGST split) and the layout is up to you.

For a shop issuing dozens of bills a day, the safest format is one you do not have to fill in by hand. If you want to try that for free, BillZap is on Google Play. It works offline and needs no sign-up, and the GST section on our home page shows what it handles.

This guide explains the rules in plain language and is not tax advice. GST rates and thresholds change; confirm anything that affects a filing with your chartered accountant.