Enabling GST e-invoicing in ERPNext is one setting; understanding what happens after you flip it is the part that protects your buyer's input tax credit. On submit, the india_compliance app posts your B2B invoice to the Invoice Registration Portal, gets back a 64-character IRN and a digitally signed QR, and stamps both onto the document — and only then is it a legal tax invoice. This guide walks the exact round-trip, the five ways it silently fails, and the period-close check that finds the invoices that never got an IRN before they cost you.
Still setting e-invoicing up?
If you haven't configured the app yet, start with the GST e-invoicing setup guide for ERPNext — this post assumes it's running and focuses on the round-trip mechanics and failure modes.
A GST invoice without a valid IRN is not a lenient technicality — under Rule 48(5) it is legally not an invoice, and your buyer's ITC hangs on it. I am Manoj, ERPNext and Frappe implementation lead at Mith Tech in Bengaluru, and getting this round-trip watertight is one of the first things we harden on any Indian implementation.
Are you even in scope?
Before the mechanics, confirm which rules bind your turnover — the mandate and the 30-day reporting restriction have different thresholds.
Enter your aggregate annual turnover and whether you raise B2B documents to see whether e-invoicing is mandatory and whether the 30-day reporting rule applies.
With AATO ≥ ₹10 crore, every B2B invoice/CN/DN must get an IRN from the IRP, and it must be reported within 30 days of the document date (in force from 1 Apr 2025, continuing FY 2026-27). Miss the window and the document cannot be reported at all.
Thresholds as of 2026-07-31: mandate > ₹5 cr AATO; 30-day reporting ≥ ₹10 cr (from 1 Apr 2025). Confirm the current CBIC/GSTN notification for your period — these have only moved downward.
Verify the current threshold for your period
The figures here are correct as of 31 July 2026 — mandate above ₹5 crore AATO, 30-day reporting at ₹10 crore and above. These have only ever moved downward, and a fresh notification can change the band mid-year. Confirm the current CBIC/GSTN position for your filing period rather than trusting any blog, including this one.
The round-trip, step by step
When you submit a B2B Sales Invoice on a configured instance, the india_compliance app runs a sequence that ends with a legally valid invoice — or does not:
- Build the JSON. The app assembles the invoice into the IRP's schema: supplier and recipient GSTINs, line items with HSN, taxable value, tax breakup, place of supply.
- Post to the IRP. It authenticates via your GSP and submits the JSON to the Invoice Registration Portal.
- Receive the IRN + signed QR. The IRP validates and returns a 64-character SHA-256 IRN plus a digitally signed QR embedding the mandated parameters (supplier GSTIN, recipient GSTIN, invoice number and date, invoice value, line-item count, main HSN, and the IRN/hash).
- Stamp the document. The app stores the IRN, QR, acknowledgement number and date on the Sales Invoice.
- Render on the PDF. The Print Format shows the IRN and QR on the face of the invoice.
Only after step 4 is the document an invoice under Rule 48(5). Skip or fail any step and you have a booked sale that is not, in law, a tax invoice — which is where your buyer's ITC gets exposed under §16(2)(a).
Where the accounting standard meets the tax rule
Revenue recognition and the tax invoice are two separate events. Under Ind AS 115 / IFRS 15, revenue is recognised when control transfers — which can precede or follow the IRP round-trip. The GST invoice validity is a tax-law condition (Rule 48), not a revenue-recognition one. The practical consequence: a period can legitimately carry recognised revenue whose underlying invoice has no IRN yet — which is exactly why the reconciliation below matters. Confirm the revenue treatment with your auditor; the IRN status does not change when revenue is booked, only whether the document is a valid tax invoice.
Where the round-trip breaks
Five failure points cover almost every real case. Each fails differently, and the fix is different — routing them correctly is the whole game.
Select where the IRP round-trip broke to get the underlying cause and the correct fix — retry, data correction, template fix, or credit note.
Pick where the IRP round-trip broke.
The one that surprises people is the PDF that has an IRN internally but doesn't show it — common when a customer insists on their own Print Format and it silently drops the QR block. The document is legally valid, but the invoice you hand over doesn't look it, and a diligent buyer will reject it. The other trap is treating a missed cancellation as an ERPNext cancel: past 24 hours the IRP will not release the IRN, so cancelling only in ERPNext leaves your books and the portal permanently out of step — the e-invoice deadlines guide covers that window in full.
Configure, verify, reconcile
Copy-paste the configuration steps, the per-document verification, the period-close reconciliation report india_compliance omits, and the habits that keep the round-trip healthy.
Set up india_compliance e-invoicing so IRN generation is automatic and every PDF carries the IRN + QR.
1. Install/enable the india_compliance app on the site.
2. GST Settings → e-Invoice:
• Enable e-Invoicing
• Set the applicable-from date matching your mandate
• Connect the GSP / e-invoice credentials (sandbox
first, then production)
3. Confirm the Sales Invoice submit hook generates the
IRN + signed QR and stores them on the document.
4. Print Format: use the e-invoice-aware format, OR add
the IRN + QR block to your custom template so both
appear on the buyer's PDF.
5. Test end to end on the sandbox IRP with a real B2B
customer GSTIN before going live.Confirm applicability, then configure
Establish which rules bind your turnover, then enable e-invoicing in GST Settings, connect the GSP credentials, and confirm the Sales Invoice submit generates the IRN and signed QR. Test the whole flow on the sandbox IRP with a real B2B GSTIN before production — the sandbox rejects the same data the live portal will.
Verify every B2B document
On each submitted B2B invoice, confirm the IRN (64 characters), the signed QR, the acknowledgement number, and an e-invoice status of Generated. If it reads Pending or Failed, open the e-invoice log for the exact IRP error — most are GSTIN, HSN or place-of-supply validation the portal enforces more strictly than ERPNext's own submit.
Render IRN and QR on the buyer's PDF
Use the e-invoice-aware Print Format, or add the IRN and QR block to your custom template. Both must appear on the face of the invoice. Lock this into your template review so a bespoke format never ships without them.
Reconcile at period close
Build a Query Report of every B2B Sales Invoice in the period whose e-invoice status is not Generated. Run it before every GST return. Each row is a booked sale with a legally invalid document and an exposed ITC — the GST return filing guide covers where these surface in GSTR-1. Resolve all of them before you file.
When accounts submit and IT owns the portal
The person submitting the invoice is in accounts; the person who set up the GSP connection and owns the e-invoice queue is in IT or with the implementation partner. The failure mode lives in that gap: an invoice submits, the IRP is briefly unreachable, no IRN comes back — and the accounts user, seeing a submitted invoice, sends the PDF to the customer. The customer's ITC is now sitting on a document that is not an invoice, and nobody notices until reconciliation or a buyer complaint.
The control that closes it is a queue nobody has to remember to check. Make the e-invoice reconciliation report a standing item on the pre-filing checklist, owned by whoever signs the GST return, and set a rule that no B2B PDF leaves the building until its status reads Generated. That turns a silent, ageing exposure into a same-day catch.
Draft policy for your finance and IT leads to ratify. No B2B invoice PDF is delivered to a customer until its e-invoice status is Generated and the IRN and signed QR appear on the document. The e-invoice queue is reviewed daily; any Pending or Failed document older than one working day is escalated. Before every GST return, the reconciliation report of non-Generated B2B invoices is run and cleared to zero. IRN cancellation is attempted only within the 24-hour window; beyond it, a credit note is raised. Confirm the reporting-period treatment with your CA before this enters an SOP.
Fix it now, or let it reconcile at close
FAQ
+Why is my e-invoice not generating in ERPNext?
Most often the IRP rejected the document on validation — an invalid recipient GSTIN, a missing or wrong HSN, or a place-of-supply mismatch — so no IRN was issued even though the Sales Invoice submitted. Open the e-invoice log for the exact IRP error, fix the data, and regenerate. Do not deliver the PDF until the IRN and QR are on it.
+What turnover makes GST e-invoicing mandatory in ERPNext?
As of 31 July 2026, e-invoicing is mandatory for B2B invoices, credit notes and debit notes where aggregate annual turnover exceeds ₹5 crore in any financial year from 2017-18 onward. The separate 30-day reporting restriction currently applies at ₹10 crore AATO and above. Confirm the current CBIC/GSTN notification for your period — these thresholds have only moved downward.
+What happens to my buyer's ITC if the IRN fails?
Without a valid IRN the document is not an invoice under Rule 48(5), so your buyer cannot claim input tax credit against it under §16(2)(a). The missing IRN is your failure as the supplier, but it lands as a cash-flow problem on the buyer, who will chase you to reissue a valid invoice.
+Can I cancel an IRN in ERPNext after generating it?
Only within 24 hours of IRN generation, which maps to the standard Cancel action. After 24 hours the IRP will not cancel the IRN, and a credit note against the reported invoice is the only correction. Cancelling only in ERPNext beyond the window leaves your books and the IRP permanently inconsistent.
+The IRN generated but the QR isn't on the printed invoice — why?
The IRN and signed QR are stored on the document, but your Print Format is not rendering them — almost always because a bespoke customer template overrides the standard e-invoice format and omits the QR block. Add the IRN and QR block to the custom template; a compliant invoice must show both on its face.
+Does e-invoicing apply to B2C sales?
The IRP mandate covers B2B documents, exports and supplies to SEZ or deemed exports — not pure B2C sales, which have a separate dynamic-QR requirement for large taxpayers. If you raise any B2B document at all, the e-invoicing mandate applies to those regardless of your B2C volume.
Related issues you may also hit
- The e-invoice 30-day and 24-hour deadline rules that decide whether a fix is a retry or a credit note.
- GST return filing in ERPNext — where a missing IRN shows up in GSTR-1.
- ERPNext GST 2026 readiness — the wider compliance checklist.
- The GST e-invoicing setup guide — first-time configuration.
Closing
The e-invoice setting is trivial to enable and the round-trip behind it is where compliance actually lives. Confirm which rules your turnover triggers, verify the IRN and QR on every B2B document before it leaves, and reconcile the failures at period close rather than discovering them in a buyer's ITC complaint. Get that rhythm right and e-invoicing becomes a background process instead of a filing-day fire.
e-Invoices failing silently and buyers chasing you over blocked ITC?
We harden your india_compliance e-invoice setup, build the reconciliation report that catches failed IRNs before filing, and lock the IRN and QR into every Print Format your customers use.