What is GST e-Invoicing?
GST e-Invoicing is a system introduced by the Government of India where businesses generate Invoice Reference Numbers (IRN) for their B2B invoices through the Invoice Registration Portal (IRP). This ensures standardised invoice data across the GST ecosystem and reduces errors in return filing.
Who needs to comply?
As of 2026, e-Invoicing is mandatory for all businesses with an aggregate turnover exceeding Rs. 5 crore in any financial year from 2017-18 onwards. The threshold has been progressively lowered since the mandate was first introduced for businesses with turnover above Rs. 500 crore in October 2020.
How does e-Invoicing work?
The process involves three key steps:
- Generate invoice data in the standard JSON schema prescribed by GSTN. Your accounting software (like ReadyBooks.ai) handles this automatically.
- Upload to IRP — the Invoice Registration Portal validates the data, generates a unique IRN, digitally signs the invoice, and returns a QR code.
- Share with buyer — the signed invoice with IRN and QR code is shared with the buyer. The IRP also pushes data to the GST portal and the e-Way bill system.
Key fields in an e-Invoice
Every e-Invoice must include: supplier GSTIN, buyer GSTIN, invoice number, invoice date, HSN/SAC codes for each line item, taxable value, and the applicable GST rates (CGST, SGST, or IGST depending on whether it is an intra-state or inter-state supply).
Common mistakes to avoid
- Incorrect HSN codes — using the wrong HSN/SAC code leads to rejection at the IRP. Always verify codes against the official HSN directory.
- Mismatched GSTINs — the buyer's GSTIN must be active and valid. Cross-check on the GST portal before issuing invoices.
- Late reporting — e-Invoices must be generated within 30 days of the invoice date. Delayed reporting can attract penalties.
- Rounding errors — GST calculations must match to the paisa. Use accounting software that handles rounding correctly.
How ReadyBooks.ai helps
ReadyBooks.ai automatically generates e-Invoice-ready data for all your B2B sales invoices. When you create an invoice, the system validates GSTIN, applies correct HSN codes, calculates GST accurately, and formats the data in the required JSON schema. You can export this data directly for upload to the IRP, or use our upcoming direct integration to generate IRN without leaving ReadyBooks.ai.
What happens if you don't comply?
Non-compliance with e-Invoicing mandates can lead to: rejection of input tax credit (ITC) by your buyers, penalties under GST law, and potential notices from the tax department during audits. It is strongly recommended to adopt e-Invoicing well before the deadline applies to your turnover bracket.