Step 1 is the generation of the invoice by the seller in his own accounting or billing system (it can be any software utility that generates invoice including those using excel or GSTN’s provided Offline Utility). The invoice must conform to the e-invoice schema (standards) that is published and have the mandatory parameters. The optional parameters can be according to the business need of the supplier. The supplier’s (seller’s) software should be capable to generate a JSON of the final invoice that is ready to be uploaded to the IRP. The IRP will only take JSON of the e-invoice.
Note: Seller should have a utility that will output invoice data in JSON format, either from his accounting or billing software or his ERP or excel/word document or even a mobile app. Those who do not use any accounting software or IT tool to generate the invoice, will be provided an offline tool to key-in data of invoice and then submit the same. The small and medium size taxpayers (having annual turnover below Rs 1.5 Crores) can avail accounting and billing system being offered by GSTN free of cost.
Step 2 is to 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 along with invoice data. The 3 parameters which will be used to generate IRN (hash) are:
i. Supplier GSTIN,
ii. Supplier’s invoice number and,
iii. Financial year (YYYY-YY). (The IRN or hash generation algorithm will be prescribed by GSTN in the e-invoice standard).
Step 3 is to upload the JSON of the e-invoice (along with the hash, if generated) into the IRP by the seller. The JSON may be uploaded directly on the IRP or through GSPs or through third party provided Apps.
Step-4: The IRP will also generate the hash and validate the hash of the uploaded json, if uploaded by the supplier. The IRP will check the hash from the Central Registry of GST System to ensure that the same invoice from the same supplier pertaining to same Fin Year is not being uploaded again. On receipt of confirmation from Central Registry, IRP will add its signature on the Invoice Data as well as a QR code to the JSON. The QR code will contain GSTIN of seller and buyer, Invoice number, invoice date, number of line items, HSN of major commodity contained in the invoice as per value, hash etc. The hash computed by IRP will become the IRN (Invoice Reference Number) of the e-invoice. This shall be unique to each invoice and hence be the unique identity for each invoice for the entire financial year in the entire GST System for a taxpayer. [GST Systems will create a central registry where hash sent by all IRPs will be kept to ensure uniqueness of the same].
Step 5 will involve sharing the uploaded data with GST and e-way bill system. More details are given in Part-B below.
Step 6 will involve returning the digitally signed JSON with IRN back to the seller along with a QR code. The registered invoice will also be sent to the seller and buyer on their mail ids as provided in the invoice.
