ReduceTAX
BlogsPricing
LoginSign Up
HomeGuidesIRN Guide
FY 2025-26 · AY 2026-27
Updated September 2026

Comprehensive Guide to Invoice Reference Number (IRN)Understanding the essentials of IRN for FY 2025-26

Explore the intricacies of the Invoice Reference Number (IRN) system, its generation, and its implications for businesses under the Indian GST framework for FY 2025-26.

Explore the Guide
1

Understanding Invoice Reference Number (IRN)


2

Hash Generation Algorithm in IRN


3

Case Sensitivity in IRN Generation


4

Parameters for Generating IRN


5

Timing of IRN Generation


6

FAQs on Invoice Reference Number (IRN)

Understanding Invoice Reference Number (IRN)

The Invoice Reference Number (IRN) is a crucial component of the e-invoicing system under GST.

  1. Definition and Purpose

    IRN is a unique identifier for each e-invoice, ensuring authenticity and traceability.

    • Implemented from October 1, 2020, for businesses with ₹500 crore+ turnover.

    • Mandatory for all B2B transactions under GST.

    • Facilitates seamless verification by tax authorities.

  2. Structure of IRN

    IRN is a 64-character alphanumeric code generated through a hash algorithm.

    • Unique for each invoice in a financial year.

    • Generated by the Invoice Registration Portal (IRP).

    • Ensures no duplication across the GST system.

  3. Legal Requirements

    IRN must be included in every invoice, debit note, or credit note.

    • Mandatory for compliance with GST regulations.

    • Facilitates input tax credit claims.

    • Non-compliance may lead to penalties under GST laws.

  4. Verification Process

    IRN allows for easy verification of invoices by tax authorities.

    • Verification can be done online or offline.

    • Ensures the genuineness of transactions.

    • Reduces the risk of fraudulent invoices.

Hash Generation Algorithm in IRN

The hash generation algorithm is fundamental to creating a unique IRN.

  1. Algorithm Overview

    Converts invoice details into a unique hash code.

    • Uses a combination of alphabets, numbers, and special characters.

    • Ensures data integrity and security.

    • Prescribed by the GST Network (GSTN).

  2. Security Features

    The algorithm ensures that the original data cannot be easily deciphered.

    • Prevents unauthorized access to invoice data.

    • Enhances the security of the e-invoicing system.

    • Complies with international data security standards.

  3. Implementation

    Implemented as part of the e-invoicing standard.

    • Mandatory for all eligible taxpayers.

    • Ensures uniformity across different GSTINs.

    • Facilitates seamless integration with accounting software.

  4. Worked Example

    Example of hash generation for an invoice.

    • Invoice Number: INV12345

    • Supplier GSTIN: 27AAACB1234F1Z5

    • Financial Year: 2025-26

Case Sensitivity in IRN Generation

The GSTN advisory on case sensitivity impacts how IRNs are generated.

  1. Advisory Details

    Effective from June 1, 2025, IRNs are case-insensitive.

    • All invoice numbers converted to uppercase.

    • Prevents duplication of IRNs.

    • Aligns with GSTR-1 treatment of invoice numbers.

  2. Impact on Businesses

    Ensures consistency in invoice reporting.

    • Reduces errors in IRN generation.

    • Simplifies compliance for businesses.

    • Enhances accuracy in GST returns.

  3. Implementation Steps

    Steps to ensure compliance with the advisory.

    • Update accounting software to handle case conversion.

    • Train staff on new IRN generation process.

    • Regularly review invoices for compliance.

  4. Benefits

    Advantages of case-insensitive IRN generation.

    • Streamlines the e-invoicing process.

    • Reduces administrative burden.

    • Improves data accuracy and reliability.

Parameters for Generating IRN

Key parameters involved in the generation of an IRN.

  1. Supplier GSTIN

    The GSTIN of the supplier is a critical parameter.

    • Ensures the IRN is linked to the correct supplier.

    • Mandatory for all e-invoices.

    • Facilitates tracking of supplier transactions.

  2. Document Number

    The unique invoice or document number.

    • Must be unique within a financial year.

    • Used to generate the hash code.

    • Ensures traceability of each transaction.

  3. Financial Year

    The financial year in 'YYYY-YY' format.

    • Ensures IRN uniqueness across financial years.

    • Facilitates year-wise tracking of invoices.

    • Important for compliance with GST regulations.

  4. Worked Example

    Example of parameter usage in IRN generation.

    • Supplier GSTIN: 27AAACB1234F1Z5

    • Invoice Number: INV12345

    • Financial Year: 2025-26

Timing of IRN Generation

When and how the IRN should be generated for compliance.

  1. Mandatory Timing

    IRN must be generated at the time of invoice issuance.

    • Applies to invoices, debit notes, and credit notes.

    • Ensures real-time compliance with GST laws.

    • Facilitates timely reporting to the GST portal.

  2. Turnover Thresholds

    Different turnover thresholds for mandatory e-invoicing.

    • ₹5 crore+ turnover: Mandatory from August 1, 2023.

    • ₹10 crore+ turnover: Required from November 1, 2023.

    • ₹100 crore+ turnover: Reporting within 30 days of issuance.

  3. Compliance Deadlines

    Key deadlines for IRN generation and reporting.

    • IRN must be generated before the invoice is shared with the buyer.

    • Reporting to IRP within 7 days for ₹100 crore+ turnover.

    • Regular updates from GSTN on compliance requirements.

  4. Worked Example

    Example of IRN generation timing for a business.

    • Business Turnover: ₹12 crore

    • Invoice Date: April 15, 2025

    • IRN Generation: April 15, 2025

FAQs on Invoice Reference Number (IRN)

What is the purpose of an Invoice Reference Number (IRN)?

The IRN serves as a unique identifier for each e-invoice, ensuring authenticity and traceability under the GST system. It helps in verifying the genuineness of transactions and facilitates compliance with GST regulations.


How is the IRN generated?

The IRN is generated using a hash generation algorithm that converts invoice details into a unique 64-character alphanumeric code. This process ensures data integrity and prevents duplication across the GST system.


Are there any changes in IRN generation for FY 2025-26?

Yes, effective June 1, 2025, the IRN generation process treats invoice numbers as case-insensitive. All invoice numbers are converted to uppercase to avoid duplication and ensure consistency.


What are the key parameters for generating an IRN?

The key parameters include the Supplier GSTIN, the unique document number (such as invoice number), and the financial year in 'YYYY-YY' format. These parameters are used to generate the hash code for the IRN.


When must the IRN be generated?

The IRN must be generated at the time of issuing an invoice, debit note, or credit note. This ensures real-time compliance with GST laws and facilitates timely reporting to the GST portal.


What are the turnover thresholds for mandatory e-invoicing?

E-invoicing is mandatory for businesses with a turnover of ₹5 crore or more from August 1, 2023. For businesses with ₹10 crore or more, it is required from November 1, 2023, and for ₹100 crore or more, reporting must be done within 30 days of issuance.


How does the hash generation algorithm enhance security?

The algorithm converts invoice details into a unique hash code, ensuring that the original data cannot be easily deciphered. This enhances the security of the e-invoicing system and complies with international data security standards.


What happens if an IRN is not generated?

Failure to generate an IRN can lead to non-compliance with GST regulations, resulting in penalties. It may also affect the input tax credit claims and the authenticity of the transaction.


Can IRN be generated offline?

No, the IRN must be generated online through the Invoice Registration Portal (IRP). However, verification of the IRN can be done both online and offline using the GST portal or mobile app.


Is there a deadline for reporting IRNs to the IRP?

Yes, for businesses with a turnover of ₹100 crore or more, invoices and credit-debit notes must be reported to the IRP within 7 days of issuance. This ensures timely compliance with GST regulations.

Related Tools & Guides

Income Tax Calculator FY 2025-26

Old vs new regime side-by-side comparison

Find a CA for ITR Filing

Verified CA assistance from ₹499

Income Tax Slab FY 2025-26

New & old regime slab rates comparison

RD Calculator

Calculate recurring deposit maturity & interest

ITR Filing Last Date FY 2025-26

Key due dates for individuals, audit & belated returns

Tax Saving FD Guide

Section 80C, best rates, lock-in & taxability
ReduceTAX - Professional Tax Services

India's trusted tax filing platform. Expert CAs, simplified process, maximum savings.

+91-9521859556

support@reducetax.in

Tax Filing

  • Self File ITR
  • CA Assisted ITR
  • NRI Tax Filing
  • Income Tax Filing
  • ITR Filing
  • Income Tax Notice Reply
  • Find a CA Near Me
  • Tax Filing Pricing

Tax Calculators

  • Income Tax Calculator
  • HRA Calculator
  • Crypto Tax Calculator
  • 80D Calculator
  • Gratuity Calculator
  • All Tax Tools

Business & Compliance

  • GST Registration
  • GST Return Filing
  • TDS Return Filing
  • Company Incorporation
  • Company Registration
  • Company Filing
  • Trademark Registration
  • Remote Accounting
  • Digital Signature (DSC)
  • All Services →

Company

  • Pricing
  • Blogs
  • All Articles
  • Contact Us

Services

  • File ITR Online
  • CA Assisted ITR
  • Income Tax Notice
  • TDS Return Filing
  • GST Return Filing
  • Company Incorporation
  • DSC Solution

Tools

  • Income Tax Calculator
  • HRA Calculator
  • Crypto Tax Calculator
  • 80D Calculator
  • 80DD Calculator
  • 80U Calculator
  • Section 80T Calculator
  • Gratuity Calculator
  • Rent Receipt Generator
  • Salary Slip Generator
  • All Tools

Knowledge Center

  • Income Tax Slab FY 2025-26
  • ITR Filing Guide
  • Old vs New Tax Regime
  • Capital Gains Tax
  • Section 80C Deductions
  • HRA Guide FY 2025-26
  • All Tax Guides →

Legal

  • Terms & Conditions
  • Privacy Policy
Recognised by
Authorised Partner — Income Tax Department, Govt. of India

Income Tax Dept.

DPIIT Recognised Startup · Startup India ID: OI-0326-9413YM

DPIIT · Startup India

iStart Rajasthan — Govt. of Rajasthan

iStart Rajasthan

© 2026 TK Business Solution Private Limited. All rights reserved.Made with ❤️ for Indian taxpayers