GST Invoice Format: Mandatory Fields, Types & Rules (2026)

16 Mandatory Fields on Every GST Tax Invoice

Under Rule 46 of the CGST Rules, every tax invoice must contain these 16 fields. Missing even one makes the invoice invalid — and the buyer loses ITC.

1. Invoice Number — Unique within a financial year, max 16 characters, alphanumeric allowed
2. Invoice Date — Cannot be backdated or future-dated beyond the date of supply
3. Supplier Name — As per GST registration certificate (REG-06)
4. Supplier Address — Principal place of business or additional place
5. Supplier GSTIN — 15-character GSTIN of the seller
6. Buyer Name — Trade name or legal name of the recipient
7. Buyer Address — Place where goods are delivered (for B2B)
8. Buyer GSTIN — Mandatory for B2B invoices; not required for B2C
9. HSN/SAC Code — 4-digit for turnover ₹1.5–5 Cr, 6-digit above ₹5 Cr
10. Description of Goods/Services — Clear description matching the HSN/SAC
11. Quantity — In the unit of measurement (NOS, KGS, LTR, MTR, etc.)
12. Unit Price — Rate per unit excluding GST
13. Taxable Value — Total value before GST (Qty × Unit Price minus any discount)
14. GST Rate & Amount — CGST + SGST (intra-state) or IGST (inter-state), shown separately
15. Total Invoice Value — Taxable value + all GST components
16. Signature/Digital Signature — Physical or DSC of authorised person

Types of GST Invoices

Invoice Type	Used When	GST Charged?
B2B Tax Invoice	Selling to a GST-registered buyer	Yes — CGST+SGST or IGST
B2C Tax Invoice	Selling to an unregistered consumer	Yes — included in price
Bill of Supply	Composition dealer or exempt supply	No — cannot charge GST
Export Invoice	Selling goods/services outside India	0% (zero-rated) or IGST (with refund)
Credit Note (CDN)	Reducing an earlier invoice value	Reduces original GST proportionally
Debit Note (DBN)	Increasing an earlier invoice value	Increases GST proportionally
Revised Invoice	Correcting a provisional invoice	As applicable

Intra-State vs Inter-State — Rate Split

Intra-state (same state): GST is split equally — CGST (Central) + SGST/UTGST (State). Example: 18% rate → 9% CGST + 9% SGST.

Inter-state (different state): Single IGST rate. Example: 18% rate → 18% IGST. No CGST/SGST split.

The Place of Supply rules determine which applies — generally the buyer's location state for goods, and the buyer's location for most services.

e-Invoice (IRN) — Additional Requirement

Businesses with turnover above ₹5 crore must generate an IRN (Invoice Reference Number) from the IRP (Invoice Registration Portal) for every B2B invoice. The IRN is a 64-character hash that cryptographically locks the invoice. Once IRN is generated, the invoice cannot be edited — changes require IRN cancellation and re-generation.

The e-invoice JSON schema (Version 1.1) adds mandatory fields beyond the 16 standard ones: supply type (B2B/B2C/SEZ/Export), reverse charge flag, and item-level tax rates. Read the full e-Invoice guide →

Invoice Series & GSTR-1 Tile 13

You must maintain a consecutive invoice series for each financial year. In GSTR-1 Tile 13 (Documents Issued), you report: document type, serial number range (From–To), total issued, and any cancelled. The count in Tile 13 must reconcile with the total invoices across all other GSTR-1 tiles.

Practice Creating GST Invoices

IndIaTaxSim's Invoice Manager lets you create B2B, B2C, Export, Credit Note, and Debit Note invoices — with automatic CGST/SGST/IGST split, HSN code lookup, IRN generation, and GSTR-1 JSON export. Try it free →