E-Invoicing Under GST: Applicability Threshold & Process
TL;DR
- E-invoicing is mandatory once aggregate turnover crosses Rs 5 crore in any financial year since 2017-18, and the obligation continues even if turnover later falls below that level.
- It applies to B2B, export, and deemed-export invoices; B2C invoices are outside the mandate.
- Taxpayers with turnover of Rs 10 crore or more must report each invoice to the government portal within 30 days, or the portal rejects it.
- An invoice without a valid IRN, where the mandate applies, is not a valid tax invoice; this can cost the recipient their input tax credit.
A surprising number of businesses that comfortably cross Rs 5 crore in turnover still generate invoices the old way, from accounting software or Excel, without realizing e-invoicing has become mandatory for them. The gap usually surfaces at the worst possible time, when a customer's finance team rejects an invoice for input tax credit because it lacks a valid IRN. Here is what actually triggers the requirement and how the process works.
Who Must Generate E-Invoices?
E-invoicing under GST is mandatory for registered businesses whose aggregate turnover has crossed Rs 5 crore in any financial year from 2017-18 onward. This is a cumulative, one-way trigger: once a business crosses Rs 5 crore in even one year, it remains covered by the mandate in all future years, regardless of whether turnover later drops below that figure. The threshold has been at Rs 5 crore since August 2023, having been progressively lowered from a much higher starting point when e-invoicing was first introduced.
The mandate covers B2B supplies, exports, and deemed exports (including supplies to SEZ units). It does not apply to B2C invoices, though businesses within the e-invoicing mandate separately need to comply with Dynamic QR Code requirements on B2C invoices above a specified value, which is a distinct requirement from IRN generation.
How the E-Invoicing Process Works
- Generate the invoice in your accounting or billing software in the standard e-invoice schema (JSON format).
- Upload it to the Invoice Registration Portal (IRP), either directly, through GST-suvidha-provider integrations, or via API from your ERP/accounting software.
- The IRP validates the invoice, checks for duplication, and generates a unique Invoice Reference Number (IRN) along with a digitally signed QR code.
- The signed invoice with IRN and QR code is returned to the supplier, who then shares this final version with the buyer. This IRN-bearing invoice is what counts as a valid tax invoice for GST purposes.
- Invoice data flows automatically to the GST return system (GSTR-1) and, where applicable, to the e-way bill system, reducing duplicate data entry.
The 30-Day Reporting Window for Larger Taxpayers
Taxpayers with an aggregate annual turnover of Rs 10 crore or more face an additional constraint: each invoice must be reported to the IRP within 30 days of the invoice date. Invoices submitted after this window are rejected outright by the portal, with no manual override. This rule pushes larger businesses to generate and report e-invoices close to the transaction date rather than batching them at month-end or quarter-end, which is a workflow change that needs to be built into the billing process, not handled as an afterthought during return filing.
Why an Invoice Without an IRN Is a Real Problem
Where e-invoicing applies, an invoice that does not carry a valid IRN is not treated as a valid tax invoice under GST law. The practical consequences fall on both sides of the transaction:
- For the buyer: Input tax credit claimed against a non-compliant invoice can be denied or challenged during assessment.
- For the supplier: Non-generation of a required e-invoice attracts penalty exposure, and the supply may not be recognised correctly in GSTR-1, creating a mismatch that surfaces during reconciliation or audit.
Because large corporate buyers increasingly reconcile input tax credit against the government's e-invoice data automatically, a missing IRN is often caught by the customer's accounts payable team before it is caught internally, which makes it a relationship problem as much as a compliance one.
Voluntary E-Invoicing Below the Threshold
Businesses below Rs 5 crore turnover are not required to generate e-invoices, but voluntary enrolment has been permitted for certain notified taxpayer categories. Businesses growing quickly toward the threshold, or those transacting heavily with large enterprise customers who prefer IRN-backed invoices for their own reconciliation, sometimes build the e-invoicing workflow into their systems ahead of the mandatory cutover, so the transition does not disrupt billing when the threshold is eventually crossed.
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Frequently Asked Questions
What is the turnover limit for mandatory e-invoicing under GST?
E-invoicing is mandatory for GST-registered businesses whose aggregate turnover has crossed Rs 5 crore in any financial year since 2017-18. The obligation is triggered by the highest turnover ever recorded from that year onward, not just the current year's figure, so a business that once crossed Rs 5 crore stays covered even if turnover later dips below that level.
Does e-invoicing apply to B2C invoices?
No. The e-invoicing mandate applies to B2B supplies, exports, and deemed exports, where the recipient is a registered person or the transaction is a supply to SEZ or an export. B2C (business-to-consumer) invoices are outside the e-invoicing framework, though businesses covered by the mandate must still comply with the Dynamic QR Code requirement on B2C invoices where applicable.
What is the IRN and how is it generated?
The Invoice Reference Number (IRN) is a unique hash generated by the government's Invoice Registration Portal (IRP) for each e-invoice submitted to it. The supplier uploads the invoice details (via their accounting/ERP software or the IRP's own tools) in the prescribed schema, the IRP validates and de-duplicates it, then returns a signed invoice with the IRN and a QR code. Only an invoice bearing a valid IRN is treated as a valid tax invoice for GST purposes once e-invoicing applies to that business.
What is the 30-day e-invoice reporting rule?
Businesses with an aggregate annual turnover of Rs 10 crore or more must report each e-invoice to the IRP within 30 days of the invoice date; invoices reported after that window are rejected by the portal. This rule pushes larger taxpayers toward reporting invoices close to real time rather than batching them at month-end, so building e-invoice generation into daily billing workflows matters more as turnover grows.
What happens if a business fails to generate an e-invoice when required?
An invoice issued without a valid IRN, where e-invoicing applies, is not treated as a valid tax invoice under GST. This can lead to denial of input tax credit to the recipient, a penalty on the supplier, and complications in claiming the transaction as a valid supply during a GST audit or assessment. Because the defect sits with the invoice itself, it is far cheaper to fix the billing process upfront than to untangle disputed invoices later.
Can a business voluntarily opt in to e-invoicing before crossing the threshold?
Yes, the GST Council has allowed voluntary e-invoicing for taxpayers below the mandatory turnover threshold in certain notified categories. Businesses expecting to cross the threshold soon, or those dealing heavily with large corporate buyers who prefer IRN-backed invoices for their own input tax credit reconciliation, sometimes opt in early to build the process before it becomes compulsory.