Understanding the Invoice Reference Number (IRN) in E-Invoicing
The Invoice Reference Number (IRN) is a unique 64-character hash assigned by the Invoice Registration Portal (IRP) for every e-invoice, debit, or credit note in India, introduced to standardize electronic invoicing. This unique identifier ensures authenticity and is mandatory at the time of document issuance. Recent advisories indicate IRN generation will become case-insensitive from June 1, 2025, with invoice numbers automatically converted to uppercase for consistency. Businesses can generate IRNs via an offline tool or API integration, with the IRP performing de-duplication checks to ensure uniqueness.
Understanding the Invoice Reference Number (IRN) in E-Invoicing
The Invoice Reference Number (IRN) is a distinct identifier assigned by the Indian government to validate and track every e-invoice. This system, which began on October 1, 2020, aims to standardize electronic invoicing across the nation. This article will explore various aspects of the Invoice Reference Number within the e-invoicing framework.
Recent Announcement > April 4, 2025: As of June 1, 2025, the Invoice Registration Portal (IRP) will process invoice numbers without considering their case for IRN generation. All invoice numbers will be automatically converted to uppercase to prevent duplicate entries and maintain uniformity.
What is an Invoice Reference Number (IRN)?
Under the e-invoicing framework, the Invoice Reference Number (IRN), also termed a hash, is a distinctive 64-character code. This code is generated by the Invoice Registration Portal (IRP) for each document, including invoices, debit notes, or credit notes. Each IRN is unique for every invoice issued by a GSTIN within a financial year across the entire GST ecosystem. Suppliers are required to include the IRN on every invoice provided to their recipients. This unique number enables tax authorities to confirm the authenticity of transactions via a central portal or an offline application, facilitating verification even without internet access.
What is the Hash Generation Algorithm in IRN?
A hash generation algorithm transforms a string of characters (comprising alphabets, numbers, and specific special characters) into a numerical sequence. The nature of this conversion ensures that the original message cannot be reconstructed from the resulting numbers. The GST Network (GSTN) defines this algorithm as a key component of the e-invoicing standard.
Case Sensitivity in IRN Generation: GSTN Advisory
The GST Network (GSTN) has announced that starting June 1, 2025, the e-Invoicing system will no longer differentiate between uppercase and lowercase letters when generating Invoice Reference Numbers (IRN). This means the Invoice Reporting Portal (IRP) will consider invoice numbers with varying letter cases as identical. To maintain uniformity and prevent duplicate IRNs, all invoice numbers, regardless of their initial formatting (e.g., "abc," "ABC," or "Abc"), will be converted to uppercase before processing. This modification ensures consistency, mirroring the existing case-insensitive treatment of invoice numbers in GSTR-1 filings.
Parameters Used for Invoice Reference Number (IRN) Generation
The IRN is created by applying a hash generation algorithm to transform specific character inputs into a numerical hash. The following three key parameters are utilized in this process:
- The supplier's Goods and Services Tax Identification Number (GSTIN).
- The unique document number issued by the supplier, such as an invoice number.
- The relevant financial year, formatted as 'YYYY-YY' (e.g., 2019-20).
When is the Invoice Reference Number (IRN) Generated?
The Invoice Reference Number (IRN) must be generated precisely when a seller issues an invoice, credit note, or debit note. This IRN system is currently active and mandatory for businesses across various annual aggregate turnover levels.
The table below outlines the key milestones and changes in the e-invoicing mandate and its applicability over time:
| Date | Key Changes |
|---|---|
| 1st Oct 2020 | E-invoicing implemented for businesses with ₹500 crore+ turnover. |
| 1 Oct 2022 | The e-Invoicing system for B2B transactions extended to taxpayers having Annual Aggregate Turnover (AATO)₹10 crore to ₹20 crore. |
| 12 Apr 2023 13 Apr 2023 | ₹100 crore+ turnover businesses required to report invoices and credit-debit notes to the IRP within 7 days from 1 May 2023. |
| 6 May 2023 | GSTN deferred the 7-day e-invoice reporting deadline by 3 months. |
| 10 May 2023 | Phase 6: ₹5 crore+ turnover businesses to issue e-invoices from 1 Aug 2023. |
| 1 Aug 2023 | E-invoicing became mandatory for businesses with an AATO of ₹5 crore or more. |
| 13 Sep 2023 | Businesses with an AATO of ₹100 crore or more required to report e-invoices to IRP within 30 days of issuance w.e.f 1st November, 2023 |
| 5 Nov 2024 | Businesses with an AATO of ₹10 crore or more required to report e-invoices to IRP within 30 days of issuance w.e.f 1st April, 2025 |
Businesses can continue to use their existing invoicing software for creating invoices within the e-invoicing framework. Nevertheless, these invoices must adhere to specific standards and parameters.
There are two primary methods for generating an IRN:
- Utilizing the dedicated Excel offline tool.
- Integrating directly with the e-invoice portal/IRP through an API or using a GST Suvidha Provider.
For additional insights, resources are available on topics such as generating IRNs in bulk on the IRP, understanding the Invoice Registration Portal, and the procedures for modifying or canceling an e-invoice.
It is important to note that regardless of the chosen method, the IRP conducts a de-duplication check. This involves verifying the newly generated IRN against the GST System's Central Registry to guarantee its uniqueness.