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Practical GST Guide

GST Invoicing Rules — Tax Invoice, E-Invoicing & Credit Notes

GST invoicing rules govern the format, content, and timeline for tax invoices, debit/credit notes, and e-invoicing. Section 31-34 of the CGST Act and Rules 46-55 prescribe mandatory fields, e-invoice thresholds, and document requirements.

Mandatory Fields
11+
Document Types
6 Types
E-Invoice
> ₹5 Cr
IRN Cancel
24 Hours

Mandatory Invoice Fields

Name, address, GSTIN of supplierLegal name as per GST registration. Trade name optional.
Consecutive serial number (max 16 chars)Unique for a financial year. Can contain alphanumeric + special chars. Must be in one or multiple series.
Date of issueDate when invoice is issued. For continuous supply: date of receipt of payment or statement date.
Name, address, GSTIN of recipient (if registered)If B2C (unregistered): name and address required only if value > ₹50,000.
HSN Code / SAC Code4 digits if turnover > ₹5 Cr, 6 digits if > ₹5 Cr (notification-based). SAC for services.
Description of goods/servicesClear description sufficient to identify the supply.
Quantity and unit (for goods)UQC (Unique Quantity Code) as per GST notification. E.g., NOS, KGS, MTR.
Total value before taxTaxable value = Transaction value minus discounts.
Tax rate and amount (CGST, SGST/UTGST, IGST, Cess)Break up of tax: CGST + SGST for intra-state, IGST for inter-state.
Place of supply (for inter-state)State name + code. Critical for determining IGST vs CGST+SGST.
Signature (digital or manual)DSC, e-signature, or manual signature. For e-invoicing: QR code serves as authentication.

GST Document Types

Tax Invoice

Section 31(1)

When: Every taxable supply of goods/services

Issuance: Before or at the time of removal of goods / delivery. For services: within 30 days of supply (45 days for banking/insurance).

Bill of Supply

Section 31(3)(c)

When: By composition dealers OR for exempt supplies

Issuance: Same timeline as tax invoice. No tax breakup shown (since no GST charged).

Debit Note

Section 34(3)

When: Taxable value or tax charged in invoice is LESS than actual

Issuance: When additional amount needs to be charged to recipient. Example: price increase after invoice issued.

Credit Note

Section 34(1)

When: Taxable value or tax charged in invoice is MORE than actual, or goods returned

Issuance: Must be issued before: (a) 30th November of following FY, OR (b) date of filing annual return — whichever is earlier.

Receipt Voucher

Section 31(3)(d)

When: Advance payment received before supply

Issuance: At the time of receipt of advance. If supply is made subsequently: issue tax invoice and adjust advance.

Refund Voucher

Section 31(3)(e)

When: Advance received but supply not made, and refund issued

Issuance: At the time of refund of advance. Used when transaction is cancelled after advance payment.

E-Invoicing Rules

Applicability

Mandatory for businesses with aggregate turnover > ₹5 Cr (from August 1, 2023). Previously: ₹10 Cr (Oct 2022), ₹20 Cr (Apr 2022), ₹50 Cr (Apr 2021), ₹100 Cr (Jan 2021), ₹500 Cr (Oct 2020). Government may further lower the threshold.

Process

Generate invoice in accounting software → Upload JSON to IRP (Invoice Registration Portal) → IRP validates and returns: IRN (Invoice Reference Number, 64-char hash), digitally signed QR code, signed e-invoice. Invoice is now valid.

IRP Portals

Primary: einvoice1.gst.gov.in (NIC). Backup: einvoice2.gst.gov.in. Private IRPs also authorized (e.g., ClearTax, Cygnet). All IRPs connect to GST system.

IRN (Invoice Reference Number)

Unique 64-character hash generated by IRP. Based on: Supplier GSTIN + FY + Document Type + Document Number. Once generated: invoice cannot be modified. Can be cancelled within 24 hours only.

Auto-population

E-invoice data auto-populates: GSTR-1 (outward supply), e-way bill Part A (if shipping details provided). No separate GSTR-1 entry needed for e-invoiced supplies.

Exemptions

Not required for: SEZ units, insurers, banking companies, GTA, passenger transport, cinema tickets, OIDAR services. Bill of Supply (composition dealers, exempt supplies): not covered.

GST Invoicing FAQs

When is a tax invoice required under GST?

A registered person must issue a tax invoice for every taxable supply of goods or services (Section 31). For goods: before or at the time of removal/delivery. For services: within 30 days of supply (45 days for banking/financial services/insurance). For continuous supply: at the time of each payment or milestone. No invoice needed for supplies below ₹200 (if recipient doesn't demand). Reverse charge: recipient must issue self-invoice within 30 days.

What is e-invoicing and who must comply?

E-invoicing is the electronic authentication of B2B/B2G invoices through the government's Invoice Registration Portal (IRP). It generates an IRN (Invoice Reference Number) and QR code for each invoice. Currently mandatory for turnover > ₹5 Cr. Process: generate invoice normally → upload to IRP via API/portal → IRP validates and returns signed invoice. Benefits: auto-populates GSTR-1 and e-way bill, reduces fraud, enables real-time tax data for government.

Can I cancel or modify an e-invoice?

Cancel: Within 24 hours of IRN generation on the IRP portal. After 24 hours: cannot cancel on IRP. Workaround: issue a credit note (which also needs to be e-invoiced) to nullify the original invoice. Modify: E-invoices CANNOT be modified once IRN is generated. If changes needed: cancel within 24 hours and re-generate, or issue debit/credit note for adjustments.

What is the time limit for issuing credit notes?

Section 34: Credit note must be issued on or before the EARLIER of: (1) 30th November of the financial year following the year of original invoice, or (2) Date of filing annual return (GSTR-9) for that year. Example: For an invoice dated 15-Aug-2025, credit note must be issued before 30-Nov-2026 or GSTR-9 filing date for FY 2025-26 — whichever is earlier. After this: no credit note can be issued and output tax cannot be reduced.

How many digits of HSN code are required on invoices?

Depends on aggregate turnover: (1) Up to ₹5 Cr: 4-digit HSN/SAC code required on B2B invoices (optional on B2C), (2) Above ₹5 Cr: 6-digit HSN/SAC code required. Notification 78/2020: made HSN mandatory on all tax invoices from April 2021. E-invoicing: 4 or 6 digits as per turnover slab. Incorrect HSN: may lead to mismatch in GSTR-1 and ITC issues for recipient.

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