GST Invoice — Format, Rules & How to Create a Compliant Invoice
By Parul Singh, GST Practitioner · GST Compliance · Updated June 2026
Table of Contents
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Mandatory GST Invoice Fields
I review 1,000+ invoices monthly. The most common mistake: missing mandatory fields. Invalid for ITC under Section 31. A GST invoice is not just a commercial document — it is a legal requirement. Without a proper invoice, your buyer cannot claim ITC, and you cannot collect GST.
Official Reference: Section 31 of the CGST Act 2017 mandates issuance of tax invoice for supply of goods and services. Rule 46 of CGST Rules prescribes the mandatory fields. Rule 47 covers the bill of supply. Rule 48 covers the revised invoice. Non-compliance can result in penalty under Section 122.
Every GST invoice must contain:
- Name, address, and GSTIN of supplier
- Name, address, and GSTIN of recipient (for B2B) or state name (for B2C)
- Invoice number (consecutive series, not broken)
- Date of issue
- Description of goods or services
- HSN/SAC code (mandatory for turnover above ₹1.5 crore)
- Quantity and unit of measurement
- Taxable value, CGST, SGST/IGST amounts
- Total invoice value (including tax)
- Place of supply (for inter-state supplies)
- Reverse charge indication (if applicable)
- Signature or digital signature of supplier
📍 Real Example — Invoice Audit — Connaught Place Service Provider
During an invoice audit for a Connaught Place consultancy, I found: 3 invoices missing the recipient's GSTIN, 5 invoices with non-consecutive invoice numbers, and 2 invoices showing CGST+SGST instead of IGST for inter-state supply. All 10 invoices were invalid for ITC — their buyers could not claim ₹45,000 in credits. We issued credit notes and re-invoiced correctly.
Types of GST Invoices
| Type | When Used |
|---|---|
| Tax Invoice | Regular B2B and B2C supply of taxable goods/services |
| Bill of Supply | Composition dealer supplies, exempt supplies |
| Receipt Voucher | Advance received before supply |
| Refund Voucher | When advance is refunded (no supply made) |
| Revised Invoice | Within 1 month of registration for pre-registration supplies |
| Self-Invoice | For RCM purchases from unregistered suppliers |
Time Limits for Issuing Invoices
| Supply Type | Time Limit |
|---|---|
| Goods (normal) | Before or at time of removal/delivery |
| Goods (continuous supply) | Before or at time of each payment |
| Services | Within 30 days of service completion |
| Services (banking/NBFC) | Within 45 days |
| Insurance | Before premium due date |
⚠️ Common Mistake: Late issuance of invoice means late reporting in GSTR-1, which means your buyer gets ITC late. This is a common source of disputes in B2B relationships. Issue invoices on the date of supply — not days or weeks later. In Delhi, I have seen suppliers who issue invoices only at month-end — this is technically wrong and can cause ITC issues for buyers.
E-Invoicing Requirements
E-invoicing is mandatory for businesses with turnover above ₹5 crore. You must generate an Invoice Reference Number (IRN) through the government portal before issuing the invoice:
- Prepare the invoice in the prescribed JSON format
- Submit to the IRP (Invoice Registration Portal)
- Receive IRN + QR code
- Print the IRN and QR code on your invoice
- Issue to buyer with IRN
Official Reference: Rule 48(4) of CGST Rules mandates e-invoicing for specified taxpayers. Notification 13/2020 (as amended) sets the threshold at ₹5 crore turnover. The e-invoice must be generated within the time limit prescribed — currently 30 days for taxpayers with turnover above ₹100 crore and 7 days for others.
📍 Real Example — E-Invoice for Okhla Manufacturer
An Okhla manufacturer with ₹8 crore turnover generates 100+ B2B invoices monthly. Process: (1) Create invoice in Tally, (2) Export as JSON, (3) Submit to IRP via API integration, (4) Receive IRN within seconds, (5) Print invoice with IRN + QR code. Total time per invoice: 2 minutes. Bulk processing: 30 minutes for 100 invoices.
Credit Notes and Debit Notes
- Credit Note: Issued when you need to reduce the invoice value (discounts, returns, deficiency in supply)
- Debit Note: Issued when taxable value or tax increases after invoice (additional charges, price revision)
- Must be issued within the same financial year or before September of next FY
- Must be reported in GSTR-1 of the month of issuance
💡 Pro Tip from Parul: I offer invoice audit and compliance review services. I check your existing invoices against Rule 46 requirements, fix non-compliant ones, and set up proper invoicing processes. Starting at ₹2,999. Call/WhatsApp: +91 95401 04776
Common GST Invoice Mistakes
- Missing GSTIN of recipient — makes invoice invalid for B2B ITC
- Wrong GST type — CGST+SGST instead of IGST for inter-state
- Non-consecutive invoice numbers — creates gaps that trigger audit
- Missing HSN/SAC codes — mandatory for turnover above ₹1.5 crore
- No place of supply — required for inter-state and services
- Not generating e-invoice — penalty for eligible taxpayers
- Late issuance — creates reporting delay in GSTR-1
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Frequently Asked Questions
What is the penalty for not issuing a GST invoice?
Under Section 122(1)(i), penalty of ₹10,000 or the tax amount, whichever is higher, for not issuing a tax invoice. For B2B supplies, this also means your buyer loses ITC, which can damage business relationships permanently.
Is e-invoicing mandatory for all businesses?
Currently mandatory for businesses with aggregate turnover above ₹5 crore in any of the previous financial years from 2017-18 onwards. Small businesses below this threshold are exempt. The threshold may be reduced further in future.
Can I issue a single invoice for multiple supplies?
Yes, you can issue a consolidated invoice for multiple supplies to the same buyer in a month. However, each supply must be listed separately with its own description, HSN code, and tax amount. Do not club different tax rate items in a single line item.
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