GST-Compliant Invoice Format: A Practical Guide (with a Free Tool)

A poorly drafted GST invoice is more than a documentation issue — it can deny your buyer their input tax credit, attract penalties under Section 122 of the CGST Act, and trigger scrutiny during GST audits. We see at least one client a quarter caught out by missing fields on supplier invoices, leading to ITC reversals worth lakhs.

This guide covers exactly what a GST-compliant tax invoice must contain, the differences between regular invoices and e-invoices, and a free online tool we operate that handles the format for you.

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What a GST tax invoice must contain

Rule 46 of the CGST Rules prescribes the mandatory particulars on every tax invoice issued by a registered person:

1. Name, address, and GSTIN of the supplier
2. A consecutive serial number — unique for each financial year, max 16 characters, alphanumeric, with dashes / slashes allowed
3. Date of issue
4. Name, address, and GSTIN / UIN of the recipient (if registered)
5. For unregistered recipients where invoice value > ₹50,000: name, address, and place of supply with state name
6. HSN code of goods or SAC code of services (digit count varies by turnover)
7. Description of goods / services
8. Quantity (and unit / UQC for goods)
9. Total value of supply
10. Taxable value (after discount)
11. Rate of tax — CGST, SGST, IGST, UGST, cess separately
12. Amount of tax charged — CGST, SGST, IGST, UGST, cess separately
13. Place of supply with state name (for inter-state supplies)
14. Address of delivery (if different from place of supply)
15. Whether tax is payable on reverse charge basis
16. Signature or digital signature of the supplier or authorised representative

For exports and SEZ supplies, additional endorsements apply: “SUPPLY MEANT FOR EXPORT ON PAYMENT OF IGST” or “SUPPLY MEANT FOR EXPORT UNDER LUT WITHOUT PAYMENT OF IGST”, etc.

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HSN code requirement — the digit count trap

The number of HSN digits required depends on turnover:

Aggregate turnover (preceding FY)	HSN digits required
Up to ₹5 Cr	4 digits (B2B), 4 digits optional (B2C)
Above ₹5 Cr	6 digits (all invoices)
Exports / Imports	8 digits

Wrong HSN digit count is one of the most common reasons for GST notice issuance. Even if your tax computation is correct, the wrong number of digits can trigger Sec 122 penalty of ₹25,000 per invoice.

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E-invoicing — who must comply

E-invoicing requires reporting invoices to the Invoice Registration Portal (IRP) before issue, which returns a 64-character IRN and a QR code that must be embedded on the invoice.

Applicability for FY 2025-26:

Aggregate turnover (any preceding FY from 2017-18)	E-invoicing applicable?
Above ₹5 Cr	Yes — mandatory for B2B, exports, SEZ, deemed exports
Up to ₹5 Cr	No (B2C anyway exempt for everyone)

Exempt categories even above the threshold: insurers, banks, NBFCs, GTAs, passenger transport service, multiplex cinema services, government departments, SEZ units (but not SEZ developers).

If e-invoicing applies and you issue an invoice without IRN, the invoice is not legally valid under GST. Your buyer cannot claim ITC; you face Section 122 penalty.

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Tax invoice vs Bill of Supply vs Receipt Voucher

Use the right document for the right transaction:

Document	When to issue
Tax Invoice	Taxable supply by a regular registered person
Bill of Supply	Exempt supply, or supply by a composition dealer
Receipt Voucher	Receipt of advance payment for goods / services
Refund Voucher	When advance is refunded
Payment Voucher	When recipient pays tax under reverse charge (RCM)
Credit Note	Reduction of taxable value or tax (post-supply)
Debit Note	Increase of taxable value or tax (post-supply)

A composition dealer issuing a tax invoice instead of a bill of supply is a Sec 122 offense. So is a regular taxpayer issuing a bill of supply for a taxable supply.

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Invoice timelines

Supply type	Invoice deadline
Goods (movement involved)	Before / at the time of removal
Goods (no movement)	Before / at the time of delivery
Continuous supply of goods	On / before issue of statement of account or payment
Services	Within 30 days from supply (45 days for banks / NBFCs / insurers)
Continuous supply of services	On / before due date of payment / completion event
Reverse charge	Within 30 days of receipt of goods / services

Late invoicing doesn’t defer GST liability — the time of supply rules under Section 12 / 13 still apply, and you can end up owing GST on a transaction you haven’t invoiced yet.

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Common invoice mistakes that cost ITC

1. Wrong GSTIN of recipient — even a single digit error means the invoice doesn’t auto-populate in your buyer’s GSTR-2B. They lose ITC. We see this most often with copy-paste from old templates.
2. Place of supply incorrect — wrong state code converts an intra-state supply to inter-state (or vice versa), leading to wrong tax charged.
3. Missing reverse charge mention — for RCM supplies, the invoice must clearly state “Tax payable under reverse charge.”
4. Sequential numbering broken — auditors will ask why invoice 045 is missing. “Cancelled” must be tracked separately.
5. HSN digits short — automatic flagging in GSTR-1; can lead to notices.
6. Missing signature — unsigned invoices are technically not valid; digital signature is fine.

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A free online tool: raisebill.com

Building a compliant invoice template manually — and then maintaining it as GST rules evolve — is non-trivial. We built raisebill.com for our own clients and then opened it as a free SaaS for any small business or professional in India.

What it does:

• Generates GST-compliant tax invoices with all 16 mandatory fields pre-validated
• Auto-applies the correct HSN digit count based on your turnover band
• Calculates CGST / SGST / IGST / cess based on supplier and recipient state codes
• Maintains a continuous serial number per FY
• Lets you save customer / item masters for fast invoicing
• Exports to PDF with embedded GST particulars
• Free to use for individual professionals and small businesses

What it does not do (yet):

• E-invoicing IRP integration (planned)
• GSTR-1 filing
• Bookkeeping

raisebill.com is operated by Pardeep Jha & Associates as a standalone product — the firm uses it internally for select clients and has made it publicly available. There’s no upsell pressure; it’s a utility, not a funnel. You can read more about how it fits into our automation practice.

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When to upgrade from a free tool

If you’re billing more than 50 invoices a month, multi-GSTIN, or above the e-invoicing threshold, a tool like raisebill.com gets you a clean format but won’t replace a full ERP / accounting system. At that volume, we typically recommend Tally, Zoho Books, or a custom Power Automate flow that reads from your CRM and pushes invoices to the IRP automatically. We’ve built several of these for clients — reach out if you want to discuss.

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How invoicing fits into broader GST compliance

A clean invoice is the first link in the GST compliance chain:

• Compliant invoice → correct GSTR-1 reporting → buyer’s GSTR-2B populates correctly → ITC flows
• Incorrect invoice → mismatch in GSTR-2B → buyer raises ITC denial dispute → relationship strain + potential commercial losses

This is why we treat invoice template review as part of every new client onboarding. If your current invoice format hasn’t been reviewed by a CA in the last two years, book a 30-minute review — we’ll send back a redlined version within 48 hours.

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Frequently Asked Questions

Is a digital signature mandatory on GST invoices?

The signature can be physical or digital, but it must be present. For e-invoices generated via IRP, the IRN itself replaces the signature requirement on the e-invoice copy.

Can I issue a single invoice with multiple HSN codes?

Yes. Each line item can have its own HSN code, rate, and tax. The summary at the bottom should show CGST / SGST / IGST per rate slab.

What’s the time limit for issuing an invoice for services?

Within 30 days of the supply being completed (45 days for banks, insurers, NBFCs). Continuous supplies follow milestone-based rules under Section 13.

Does a freelancer earning ₹15 lakh need GST registration?

For services, the threshold is ₹20 lakh aggregate turnover (₹10 lakh in special category states). At ₹15L, GST registration is not mandatory, but voluntary registration may make sense if your B2B clients want to claim ITC on your fees.

Is raisebill.com really free? What’s the catch?

Yes, it’s free for the core invoice generation use case. It’s operated by Pardeep Jha & Associates — we built it internally and opened it up as a community utility. No catch; the firm makes its money from advisory and compliance work, not from the tool.

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Related reading

• Compliance Calendar FY 2025-26
• GST Amnesty Scheme (Sec 128A): How to Apply
• TDS Rate Chart FY 2025-26
• See our automation practice for custom invoicing workflows beyond raisebill.com