e-Invoice Reference Number (IRN): Format, Generation, Validation & Verification
Quick Answer
The Invoice Reference Number (IRN) is a unique 64-character hash generated by the Invoice Registration Portal (IRP) for every validated e-invoice. It's computed using the supplier's GSTIN, invoice number, financial year, and document type, and once assigned, it becomes the legal proof that an invoice has been reported and validated under GST. As of 2026, businesses with aggregate annual turnover of ₹5 crore or more must generate IRNs for B2B, export, and SEZ invoices, and rules around Ship-to GSTIN and reporting timelines have recently changed.
Every valid e-invoice under GST hinges on one thing: the IRN. Without it, an invoice — however correctly drafted — isn't recognised as a valid tax document for B2B supply. This guide explains exactly what the IRN is, how it's structured, how it gets generated and validated, how to verify one, and the rule changes businesses need to track in 2026.
What Is an IRN Under GST?
The Invoice Reference Number is a unique identifier assigned by the Invoice Registration Portal to every e-invoice that passes validation. It's part of the broader e-invoicing framework administered by GSTN, the technology backbone behind GST compliance. If you're new to GST terminology generally, our explainer on what GST stands for and means is a useful starting point before diving into e-invoicing specifics.
Who Needs to Generate an IRN?
Any GST-registered business whose aggregate annual turnover has crossed ₹5 crore in any financial year since 2017-18 must generate an IRN for eligible B2B invoices, exports, and supplies to SEZ units. Businesses below this threshold, along with certain exempt categories such as banking companies, insurers, NBFCs, GTAs opting for the forward charge exemption, and government departments, are outside the mandate.
Format and Structure of the IRN
The IRN is a 64-character alphanumeric hash generated using the SHA-256 algorithm. It's derived from four inputs combined together:
- Supplier's GSTIN
- Document type (invoice, credit note, or debit note)
- Document number
- Financial year of the document
Because the hash is derived from these fields, the same combination can never generate two different IRNs — which is also why duplicate invoice numbers within a financial year get rejected outright.
Latest Updates on IRN Rules (2026)
| Effective Date | Update |
|---|---|
| 1 August 2026 | Ship-to GSTIN becomes mandatory in the Generate IRN and e-Way Bill by IRN APIs whenever Ship-to details are present. "URP" must be entered when the consignee is unregistered. This date was deferred from the originally notified 15 June 2026. |
| 1 August 2026 | A Voluntary Closure facility for e-Way Bills goes live alongside the IRN and e-Way Bill API changes, allowing early closure of a shipment's e-way bill. |
| Ongoing in FY 2026-27 | The 30-day reporting restriction continues to apply: taxpayers with AATO of ₹10 crore or more cannot report invoices, credit notes, or debit notes to the IRP for IRN generation once they are older than 30 days from the document date. |
| From April 2025, continuing in 2026 | The e-invoicing turnover threshold stands at AATO of ₹5 crore or more in any financial year from 2017-18 onward, bringing a wider base of mid-sized businesses under the IRN mandate. |
| 2026 | The signed QR code returned with the IRN must be mandatorily printed on physical invoice copies for businesses above the applicable threshold. |
Because these API and payload-level changes affect ERP and billing software directly, it's worth checking our roundup of latest GST news and updates and the official GST notifications summary regularly, so your invoicing setup doesn't fall out of sync with what the IRP expects.
How an IRN Is Generated — Step by Step
The generation of an IRN follows a fixed sequence as part of the broader GST procedure for e-invoicing:
- Your billing or ERP software prepares the invoice data in the notified JSON schema
- The JSON is submitted to the IRP, either directly or through a GSP/API integration
- The IRP validates mandatory fields, GSTINs, and checks for a duplicate invoice number
- On successful validation, the IRP computes the IRN using the SHA-256 hash of the key fields
- The IRP digitally signs the invoice, generates a QR code, and returns both to the supplier
IRN Validation Checks Performed by the IRP
Before assigning an IRN, the portal checks that the supplier and buyer GSTINs are active and correctly formatted, that the invoice number and financial year combination hasn't already been used, that HSN/SAC codes are valid, and that tax computations on each line item are internally consistent with the taxable value and applicable rate. Any failure at this stage results in a rejection, not a partial IRN.
How to Verify an IRN
An IRN can be verified in a few ways: by scanning the QR code printed on the invoice, which decodes key invoice details and confirms it was signed by the IRP; through the "Verify e-Invoice" search function on the government e-invoice portal, entering either the IRN or the invoice details; or, for recipients, by checking that the invoice appears correctly in their Invoice Management System (IMS), which only reflects invoices carrying a valid IRN.
IRN and e-Way Bill
When goods need to move, an e-way bill can be generated using the IRN itself, pulling in the invoice data already validated by the IRP rather than requiring separate entry. This connects directly to the underlying e-way bill rules and compliance requirements, and for businesses consolidating multiple invoices into a single shipment, our guide on how to generate a consolidated e-way bill explains the process.
IRN Data Flow into GSTR-1 and GSTR-3B
Once an IRN is generated, the invoice details auto-populate into GSTR-1, and this data subsequently affects output liability and matched credit when filing GSTR-3B. For a full picture of how these periodic filings connect to each other, see our overview of GST returns.
IRN and GST Electronic Ledgers
Tax amounts tied to a validated IRN eventually reflect in your GST electronic ledgers once the relevant returns are filed. Errors carried forward from an incorrectly validated IRN can distort these ledger balances, which is why catching mistakes at the IRN stage matters more than fixing them later.
Cancelling or Correcting an IRN
An IRN can be cancelled within a limited window from the time of generation, provided any linked e-way bill hasn't already been used for transport. Once that window closes, or if the invoice has already been acted upon by the recipient, the correction must be made through a credit note or debit note instead of a straight cancellation.
Common IRN Errors and How to Fix Them
| Error | Fix |
|---|---|
| Duplicate IRN request | Check whether the invoice number was already reported; reuse the existing IRN instead of resubmitting |
| Invoice older than 30 days rejected | Applicable to AATO ₹10 crore+ taxpayers; ensure invoices are reported to the IRP within 30 days of the invoice date |
| Missing Ship-to GSTIN | Populate ShipDtls.Gstin with the correct GSTIN, or "URP" if the consignee is unregistered, as required from 1 August 2026 |
| Invalid buyer/seller GSTIN | Verify GSTIN status on the GST portal before invoice generation |
| Tax calculation mismatch | Recheck rate and taxable value against each line item for rounding or rate-mapping errors |
Legal Framework Governing IRN
IRN generation is mandated under rules notified within the broader GST law framework, with GSTN responsible for the technical infrastructure and periodic advisories that adjust schema, thresholds, and validation rules.
Getting IRN rejections or unsure if the August 2026 Ship-to GSTIN change affects you? Let EasyTax review your setup.
How EasyTax Helps
EasyTax's GST and tax compliance services cover ongoing e-invoicing support, including IRN error resolution and keeping your billing system aligned with the latest IRP rule changes.
Frequently Asked Questions
What is the difference between IRN and e-invoice?
The e-invoice is the full digitally signed document, while the IRN is the unique 64-character reference number assigned to it by the IRP. The IRN is one component embedded within the validated e-invoice.
Can two invoices have the same IRN?
No. Because the IRN is a hash of the supplier GSTIN, document type, document number, and financial year, no two distinct invoices can generate the same IRN.
What is the new Ship-to GSTIN rule from August 2026?
From 1 August 2026, whenever Ship-to details are present in an invoice requiring an e-way bill, the Ship-to GSTIN must be included in the Generate IRN and e-Way Bill by IRN APIs, using "URP" if the consignee is unregistered.
Who is exempt from generating an IRN?
Banking companies, insurers, NBFCs, certain GTAs, SEZ units (as recipients, in specific cases), and government departments are among the categories currently exempt from mandatory e-invoicing, regardless of turnover.
Can I generate an IRN for an invoice older than 30 days?
If your AATO is ₹10 crore or more, invoices, credit notes, and debit notes older than 30 days cannot be reported to the IRP, and no IRN can be generated for them. Taxpayers below this threshold aren't currently subject to this restriction.
Conclusion
The IRN is what turns a regular invoice into a legally valid, government-recognised GST document — and it's increasingly tied into e-way bills, GSTR-1, IMS, and GST ledgers. With rule changes like the mandatory Ship-to GSTIN taking effect from 1 August 2026, businesses need to keep their billing software current and their IRN generation process error-free to avoid disruptions in invoicing and goods movement.
Let EasyTax handle your e-invoicing, IRN generation, and GST compliance end to end.
Reviewed by CA Pritam Sharma, EasyTax Global IT Solutions Pvt. Ltd.