Invoice Reference Number (IRN): Format & update?

What is the Invoice reference number (IRN)?

The Invoice Registration Portal (IRP) using a hash generation algorithm, under the new e-invoicing system will generate a unique number for each document such as an invoice or debit or credit note submitted on GST Portal or e-way bill portal then this generated unique number or hash will become the IRN (Invoice Reference Number) of the e-invoice

This shall be unique to each invoice and hence be the unique identifier for each invoice for the entire financial year in the entire GST System for a taxpayer. And the GST Systems will create a central registry where hash sent by all IRPs will be kept to ensure the uniqueness of the same.

What are the parameters to generate IRN (HASH)?

You can generate the unique Invoice Reference Number (IRN) (in technical terms hash of 3 parameters using a standard and well-known hash generation algorithm e.g. SHA256). This is an optional step, The seller can also generate this and upload it along with invoice data. The 3 parameters which will be used to generate IRN (hash) are:

  1. Supplier GSTIN,
  2. Supplier’s invoice number and,
  3. Financial year (YYYY-YY).  (The IRN or hash generation algorithm will be prescribed by GSTN in the e-invoice standard). 

What is the hash generation algorithm in IRN?

A hash generation algorithm is a function that converts a message or a string consisting of characters (alphabets + numbers + certain special characters) into a series of numbers such that the resulting numbers cannot indicate the original message.

What is the Format of Invoice Reference Number (IRN)?

  • Each Invoice uploaded by the taxpayer will get the unique number called an Invoice Reference Number (IRN).
  • IRN is of 64 Characters length.
  • This IRN is a unique number in the GST system, irrespective of the taxpayer, financial year and document type.
  • IRN is generated by the e-invoice system once the taxpayer uploads the invoice details.
  • IRN can also be prepared by the taxpayer and uploaded with the invoice details. The e-invoice system verifies this and accepts it accordingly.
  • IRN is generated using the computer algorithm (RSA256) based on the combination of the Supplier GSTIN, Document Type, Document Number and year of the Invoice (Financial Year).
  • IRN is hash of Supplier GSTIN + Fin. Year + Doc Type + Doc Number.
  • Financial Year is calculated based on the date of the invoice. That is, the financial year starts with 1st April and ends on 31st March and represented as YYYY-YY. If the date is 03.01.2020, the financial year is 2019-20.
  • Document types are INV for Invoice, CRN for Credit Note, DBN for Debit Note.
  • Document Number is a number printed on the Document, being issued to the purchaser, and it is to be of a maximum of 16 alphanumeric and / -.
  • The prefixing zeros, / – are ignored. However, the appearance of these characters in the middle and suffixing places is accepted as it is.
  • Using the above points, the taxpayer can generate the IRN by self.
  • For example, a taxpayer with 06AAAAA9999A19N has issued the Invoice with Number ABC01234 on 12.12.2019 to his supplier, the string used for hashing is
  • 06AAAAA9999A19N2019-20INVABC01234.
  • Removal of prefixing ‘o’,’-‘,’/’: If the invoice number is 01234 or /AB123 or -1234, then 1234 or AB123 or 1234 is used for hashing.
  • In case the invoice number is AB/123 or AB-123 or AB0123, then they are taken as it is.

Can a taxpayer generate an e-way bill using IRN?

Yes, there will be one more API, released shortly, to generate the e-way bill based on IRN and Part-B details.

Who can generate IRN from the e-invoicing system?

Presently, the taxpayers who have been notified. That is, taxpayers whose turnover is more than Rs 500 Crores and registered GSPs can generate IRN only.

Whether the IRN is to be captured in the Supplier’s ERP?

The IRN (hash) will be generated by the GST System using GSTIN of supplier or document creator, financial year and the unique serial number of the document/invoice. The IRN can also be generated by the seller.

The serial number of invoices will be unique for a GSTIN for a Fin Year and the same has to be captured by the Supplier’s ERP.

Then the supplier has to keep the IRN against each of its invoices. It will be advisable to keep the same in the ERP as an invoice without IRN will not be a legal document.

One Reply to “Invoice Reference Number (IRN): Format & update?”

  1. Pawan Kumar

    Hi Mayur, Thanks for information, I have one quention you have mentioned 2 lines for IRN generation algo. Which one algorithm is used.

    Invoice Reference Number (IRN) (in technical terms hash of 3 parameters using a standard and well-known hash generation algorithm e.g. SHA256)

    IRN is generated using the computer algorithm (RSA256)

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