GST Invoice Format in India

A GST invoice in India is not just a bill — it is a statutory document under Rule 46 of the CGST Rules, 2017. Get the format wrong and your buyer cannot claim input tax credit, your books fail a GST audit, and in the worst case you face a penalty under Section 122. The good news: the format itself is straightforward, and a clean invoice template covers 99% of small and mid-sized businesses without needing accounting software.

This guide walks through what a compliant GST invoice must contain, when CGST, SGST, and IGST apply, how HSN and SAC codes work, when e-invoicing becomes mandatory, and how to generate a compliant invoice for free in under a minute using our Invoice Generator.

What goes on a GST tax invoice

Rule 46 of the CGST Rules lists 16 fields that every tax invoice must carry. In practice, a working invoice template needs the following blocks:

Supplier block (you):

• Legal name and trade name of your business
• Full address of the place of business
• GSTIN — your 15-character GST registration number
• State and state code
• Contact details (optional but useful)

Invoice block:

• Invoice serial number — unique, consecutive, alphanumeric, maximum 16 characters, and reset only at the start of a financial year
• Invoice date
• Place of supply (state + state code) — this is what determines whether you charge CGST + SGST or IGST
• Reverse charge applicability — explicit “Yes” or “No”

Recipient block (your customer):

• Name and address
• GSTIN — mandatory if the customer is GST-registered (B2B)
• For unregistered customers (B2C), the recipient address is mandatory only if the invoice value exceeds ₹50,000

Line items table:

• Serial number
• Description of goods or services
• HSN code for goods, SAC code for services
• Quantity and unit (for goods)
• Rate per unit
• Total value
• Discount (if any)
• Taxable value (after discount)
• GST rate
• Tax amount split into CGST + SGST/UTGST (intra-state) or IGST (inter-state), plus cess where applicable

Totals block:

• Total taxable value
• Total CGST, SGST/UTGST, IGST, and cess
• Grand total in figures
• Grand total in words — required for cheque-style legal clarity
• Signature or digital signature of the supplier or an authorised representative

If you are issuing the invoice as PDF, “signature” can be a typed name, a scanned signature image, or a digital signature certificate (DSC) — the rule simply says signed, not wet-signed.

CGST + SGST vs IGST: who pays what

This trips up most first-time GST filers. The rule is mechanical once you know it:

• Intra-state supply (supplier and place of supply in the same state) → charge CGST + SGST (or CGST + UTGST for union territories). Each is half the total GST rate. So 18% GST splits into 9% CGST + 9% SGST.
• Inter-state supply (supplier in one state, place of supply in another) → charge IGST at the full rate. The 18% becomes 18% IGST, single line.

A few practical edge cases:

• For services, the place of supply is usually the recipient’s location (Section 12 of the IGST Act). A Bengaluru designer billing a Mumbai client charges IGST.
• For goods, place of supply is wherever the goods are delivered. A Surat trader shipping to a buyer in Surat charges CGST + SGST; same trader shipping to Pune charges IGST.
• Exports are zero-rated. You either supply under a Letter of Undertaking (LUT) with no tax, or pay IGST and claim a refund.
• Reverse charge flips the obligation — the recipient pays the GST instead of the supplier. You still issue an invoice; you just mark “Reverse charge: Yes” and do not collect the tax.

HSN and SAC codes

Every line item must carry an HSN code (for goods) or SAC code (for services). The number of digits required depends on your aggregate turnover in the previous financial year:

Aggregate turnover (previous FY)	HSN/SAC digits required
Up to ₹5 crore	4 digits (B2B mandatory; B2C optional)
Above ₹5 crore	6 digits mandatory on all invoices

Common examples:

• 9954 — Construction services
• 9983 — Other professional, technical, and business services (consulting, design, advisory)
• 9987 — Maintenance, repair, installation
• 998314 — IT consulting (6-digit)
• 998313 — Software development (6-digit)
• 8517 — Telephones, smartphones, communication apparatus
• 6109 — T-shirts, singlets, vests, knitted or crocheted

The CBIC publishes the full HSN/SAC list, but most small businesses use the same two or three codes across every invoice. Find yours once, save it in your template, and move on.

When e-invoicing kicks in

E-invoicing is the system where you upload the invoice to the Invoice Registration Portal (IRP), get back an IRN (Invoice Reference Number) and a QR code, and embed both on the PDF before sending it to the buyer. As of August 2023, e-invoicing is mandatory for any business with aggregate turnover above ₹5 crore in any previous financial year from 2017-18 onwards.

If your turnover is below ₹5 crore, you do not need e-invoicing — a regular GST invoice PDF (signed, with all Rule 46 fields) is fully compliant. Most freelancers, consultants, and small businesses fall into this bucket.

The ₹5 crore threshold has dropped steadily since e-invoicing started at ₹500 crore in 2020, so if you are anywhere near the cutoff it is worth keeping an eye on. The CBIC notifications usually give 90 days’ notice before a new threshold takes effect.

Time limit to issue an invoice

• Goods: before or at the time of removal of goods (when goods involve movement) or delivery (when they don’t).
• Services: within 30 days of supply of service. For financial services from banks, NBFCs, insurance, this extends to 45 days.
• Continuous supply (subscriptions, retainers, AMC contracts) — invoice on or before the due date of payment as per contract.

Late invoicing is a Section 122 offence and triggers a penalty of ₹10,000 or the tax involved, whichever is higher. Issue on time, even if payment is delayed.

Numbering rules that catch people out

• The serial number must be consecutive — no gaps. If you cancel an invoice, you cannot reuse the number; you issue a credit note.
• It must be unique within a financial year. Most businesses reset to 1 (or to a prefix like 2025-26/001) on 1 April.
• You can use a prefix that identifies your branch or business unit, as long as the total length stays within 16 characters.
• For separate series, you can run multiple parallel series (one for goods, one for services, one for export) — each must be internally consecutive.

A common, clean pattern: INV/2025-26/0042. The financial year is obvious to a GST officer, the number is unambiguous, and a quick visual scan tells you how many invoices you have issued this year.

Generate a GST invoice in under a minute

If you do not want to set up dedicated accounting software just to send a clean invoice, our free invoice generator covers the entire Rule 46 format and exports an A4 PDF with no signup and no watermark.

What it does:

• Two-column header for your business details (with GSTIN field) and client details
• Currency defaults to INR with ₹ symbol and Indian comma grouping (1,00,000 not 100,000); switch to USD/EUR/GBP for international clients
• Line items table with description, HSN/SAC, quantity, rate, and per-line tax
• GST mode — toggle CGST + SGST split or IGST single line based on the place of supply
• Tax rate per line so you can mix 18% services with 12% goods on the same invoice
• Place of supply field that drives the CGST/SGST vs IGST logic automatically
• Total in words field (Indian numbering — lakhs and crores)
• Reverse charge checkbox
• Notes field for payment terms, UPI ID, NEFT/RTGS bank details, IFSC code
• One-click A4 PDF export, generated client-side — the invoice never touches our servers

The flow:

1. Open the Invoice Generator.
2. Fill in your business block (the GSTIN goes in the dedicated field).
3. Fill in the client block. If they have a GSTIN, add it.
4. Set Place of supply to the client’s state. The tool will pick CGST + SGST or IGST based on whether your state and theirs match.
5. Add line items. Each item gets a description, HSN/SAC code, quantity, rate, and tax rate.
6. The totals, including tax-component breakdown and amount in words, fill themselves.
7. Add a note with your payment instructions (UPI ID, account number, IFSC).
8. Download PDF.

The output is a clean A4 portrait PDF that any GST-registered buyer can drop into their accounting system and claim input tax credit against. No watermark, no upsell.

A complete worked example

A consulting firm in Bengaluru (Karnataka, state code 29) is invoicing a client in Mumbai (Maharashtra, state code 27) for ₹1,00,000 of professional services at 18% GST.

Because Karnataka ≠ Maharashtra, this is an inter-state supply → IGST applies.

• Description: “Strategy advisory — May 2026 retainer”
• SAC: 9983
• Taxable value: ₹1,00,000
• IGST @ 18%: ₹18,000
• Grand total: ₹1,18,000
• In words: “One Lakh Eighteen Thousand Rupees Only”

If the same firm invoiced a Bengaluru-based client for the same amount, the tax line splits:

• CGST @ 9%: ₹9,000
• SGST @ 9%: ₹9,000
• Grand total: ₹1,18,000

Same total, different split. The grand total in figures and words stays identical — Indian numbering, one lakh eighteen thousand.

Common mistakes that fail GST audits

• Missing or wrong GSTIN. Even one transposed digit invalidates input tax credit for your buyer.
• HSN/SAC missing on B2B invoices when turnover crosses ₹5 crore.
• Wrong place of supply. Charging CGST + SGST on an inter-state supply (or vice versa) means filing a credit note and re-issuing the invoice.
• Non-consecutive serial numbers. Gaps trigger questions during audits and require you to produce cancelled-invoice records.
• Amount in words missing. Surprisingly common. Always include it.
• Reverse charge not flagged when applicable (e.g. on services from an unregistered supplier above the threshold, or specified categories like goods transport agency services).
• Date format ambiguity. Use DD-MM-YYYY or DD/MM/YYYY consistently. ISO format works too. Never MM/DD/YYYY — confusion with US format causes audit pain.

When to upgrade to accounting software

The free generator covers compliance and printing. You will outgrow it when you need:

• GSTR-1 auto-filing (the monthly return that lists every outward supply)
• Recurring invoices and subscription billing
• Customer ledgers and aging reports
• e-Invoicing IRN generation (mandatory above ₹5 crore turnover)
• Multi-user access with role-based permissions

At that point, look at Zoho Books, TallyPrime, ClearTax, RazorpayX Books, or Vyapar. Until then, a clean PDF invoice with the right fields does the job — and that is exactly what our Invoice Generator is for.

Quick reference

Field	Required?	Notes
Supplier GSTIN	Yes	15-character
Recipient GSTIN	Yes for B2B	Skip for B2C
Invoice serial number	Yes	Max 16 chars, consecutive, unique per FY
Invoice date	Yes	DD-MM-YYYY
Place of supply	Yes	Determines CGST+SGST vs IGST
HSN/SAC code	Yes (B2B)	4 digits up to ₹5 cr turnover; 6 digits above
Description	Yes	Per line item
Taxable value	Yes	After discount
Tax split (CGST/SGST or IGST)	Yes	Based on place of supply
Cess	If applicable	Tobacco, sin goods, motor vehicles
Reverse charge flag	Yes	”Yes” or “No”
Amount in words	Yes	Indian numbering — lakhs/crores
Signature	Yes	Typed, scanned, or DSC

Generate one now: Invoice Generator on TheToolBus — free, no signup, A4 PDF, INR by default.