Each Invoice uploaded by the tax payer will get the unique number called as Invoice Reference Number (IRN).
IRN is of 64 Characters length.
This IRN is unique number in the GST system, irrespective of tax payer, financial year and document type.
IRN is generated by the e-invoice system once the tax payer uploads the invoice details.
IRN is generated using the computer algorithm (SHA-256) 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 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 maximum of 16 alphanumeric and / -.
Document number should not be starting with 0, / and -. Also, alphabets in document number should not have alphabets in lower cases. If so, then request is rejected.
For example, tax payer with 01AAAAA9999A19N has issued the Invoice with Number ABC01234 on 12.12.2019 to his supplier, string used for hashing is