Two clocks run on every GST e-invoice, and missing either one turns a data-entry slip into a tax loss. You have 30 days from the invoice date to report a B2B document to the IRP, and just 24 hours to cancel an IRN once generated. Blow the 30-day window and the invoice can never be reported — it is treated as never issued, and your buyer's input tax credit on it is gone. This guide explains both windows, how ERPNext enforces them, and the ageing report that catches an invoice before it falls off the cliff.
Need the round-trip mechanics first?
This post assumes IRN generation is working. If e-invoices are failing to generate at all, start with the GST e-invoicing IRP round-trip guide — deadlines only matter once the round-trip runs.
The 30-day window is the cruelest rule in GST because nothing stops you missing it — the invoice sits happily in your books, valid-looking, until the day it becomes permanently unreportable. I am Manoj, ERPNext and Frappe implementation lead at Mith Tech in Bengaluru, and this is the timing trap I see catch finance teams who batch e-invoicing to month-end.
The 30-day reporting window
From 1 April 2025, taxpayers with aggregate annual turnover of ₹10 crore or more must report each invoice, credit note and debit note to the IRP within 30 days of the document date. This continues in FY 2026-27 with no announced relaxation. The consequence of missing it is absolute: after 30 days the IRP will not accept the document for IRN generation at all. No IRN means it is not a valid tax invoice under Rule 48(5), which means — for GST purposes — it was never issued, and your buyer cannot claim ITC against it.
Enter your turnover and how many days old an invoice is to see whether the 30-day rule binds you and how much reporting window remains.
Comfortable window remaining, but report and verify the IRN now — a pending IRN that sits is how invoices quietly age past day 30.
30-day reporting: AATO ≥ ₹10 cr, from 1 Apr 2025 (as of 2026-07-31). IRN cancellation: within 24 hours only. Confirm the current CBIC/GSTN notification for your period.
The danger is how ordinary an unreported invoice looks. It sits in your Sales Invoice list, submitted, apparently fine. Nothing in the default interface counts down the days. The first time most teams feel the 30-day rule is when a buyer calls about ITC they cannot claim — at which point the window is already closed and the only remedy is commercial.
Back-dating silently burns the window
The 30 days run from the invoice date, not the date you create the document in ERPNext. Raise an invoice today dated three weeks ago and you have only nine days of reporting window left. This is the same class of trap as backdated stock entries — a past date that quietly changes what is still possible. Treat every back-dated invoice as an urgent reporting item.
The 24-hour cancellation window
Once an IRN is generated, it can be cancelled on the IRP only within 24 hours. Inside that window, cancellation is clean — it maps to the ERPNext Cancel action and leaves no permanent trace. Outside it, the IRN is fixed forever, and the only way to correct a reported invoice is a credit note (which is itself an e-invoice needing its own IRN). These two windows interact: catch a mistake in the first day and it vanishes; catch it on day two and it becomes a permanent credit-note trail in your GSTR-1.
Which correction do you actually need?
The right response depends entirely on how old the IRN is and whether the 30-day window is still open.
Select the correction you need to make to see whether it is a clean IRN cancel, a credit note, an amendment note, or a document that can no longer be reported.
Pick the correction you need to make.
The mistake that costs the most is treating a post-24-hour correction as an ERPNext cancel. The button may appear to work, but the IRP still holds the original IRN — so the portal and your books diverge, and your GST return will not reconcile. Past 24 hours, the discipline is always: credit note against the reported invoice, then a corrected invoice if needed, with every note carrying its own IRN. The GST return filing guide covers how these net out in the return.
Monitor, correct, prevent
Copy-paste the ageing report that surfaces invoices nearing day 30, the clean 24-hour cancel steps, the post-24-hour credit-note path, and the habits that keep documents off the cliff.
The report that surfaces every invoice ageing toward day 30 before it falls off the cliff.
Report Builder / Query Report → Sales Invoice
Filters:
• recipient GSTIN not blank (B2B)
• einvoice_status != "Generated"
• posting_date within the last 30 days
Computed column:
days_remaining = 30 - (today - posting_date)
Sort: days_remaining ascending
Rows near the top are about to become unreportable.
Run daily. A pending IRN with 3 days left is an
emergency; the same row at day 31 is a lost ITC and a
commercial conversation.Report same-day, not at month-end
Generate the IRN at submit. Batching e-invoicing to a monthly run is how documents drift toward day 30 unnoticed. Same-day reporting keeps every invoice comfortably inside both windows and turns the deadlines into non-events.
Run the ageing report daily
Build a report of every B2B invoice whose IRN is still pending, with a computed days-remaining column sorted ascending. The rows at the top are about to become unreportable. This is the single control that converts the 30-day cliff into a managed queue — the same daily-reconciliation discipline as bank reconciliation.
Correct by the clock
Wrong invoice under 24 hours old — cancel the IRN and re-report. Older than 24 hours — credit note, then corrected invoice, each with its own IRN. Verify the cancel actually took on the IRP, not just in the ERPNext UI.
Guard against back-dating
Any invoice dated earlier than today consumes its 30-day window from the invoice date. Flag back-dated invoices for immediate reporting, and question why a document is being dated into the past at all — it is usually a sign of a process running behind, which is the real thing to fix.
When sales dates the invoice and finance reports it
The person choosing the invoice date is often in sales or operations, dating it to when the work happened. The person generating the IRN is in finance, days later. Between them, the 30-day clock is already running and neither owns it — so a back-dated invoice can arrive on finance's desk with a week of window already gone, and a busy month can push a document past day 30 before anyone reconciles.
The fix is to make the window visible and owned. The ageing report goes to whoever runs the GST return, daily, and any invoice under five days of remaining window is escalated the same day. Pair it with a standing rule that e-invoicing happens at submit, not in a month-end batch — the batch is precisely what lets documents age unnoticed.
Draft policy for your finance and sales leads to ratify. B2B invoices are reported to the IRP at submit, on the same day, not batched to month-end. A daily ageing report lists every pending-IRN B2B invoice by remaining window; any document with fewer than five days is escalated to the GST-return owner immediately. IRN cancellation is attempted only within 24 hours; beyond it, corrections are made by credit note. Back-dated invoices are flagged for same-day reporting and their reason recorded. Confirm the current reporting threshold and any period-specific relaxation with your CA before this enters an SOP.
Report same-day, or manage a window
FAQ
+What is the 30-day rule for e-invoices in India?
Taxpayers with aggregate annual turnover of ₹10 crore or more must report each B2B invoice, credit note and debit note to the IRP within 30 days of the document date. In force from 1 April 2025 and continuing FY 2026-27. After 30 days the IRP refuses the document, so no IRN can be generated and it is treated as never issued for GST.
+What happens if I miss the 30-day e-invoice reporting window?
The invoice can no longer be reported to the IRP, so it never gets a valid IRN and is not a legal tax invoice under Rule 48(5). Your buyer cannot claim input tax credit against it, and the only remaining route is issuing a fresh, current-dated invoice — with the pricing and relationship consequences that carries.
+Can I cancel an IRN in ERPNext after 24 hours?
No. An IRN can only be cancelled on the IRP within 24 hours of generation. After that the IRN is permanent, and the only correction is a credit note against the reported invoice — which is itself an e-invoice with its own IRN. Cancelling only in ERPNext beyond the window leaves your books and the IRP inconsistent.
+Does the 30-day window run from the invoice date or the ERPNext creation date?
From the invoice date. If you back-date an invoice, the window is already partly used the moment you create it — an invoice dated 25 days ago has just 5 days of reporting window left. Treat every back-dated document as an urgent reporting item.
+How do I correct a value on an already-reported e-invoice?
You cannot edit a reported invoice — its IRN fixes it in place. A value reduction is a Credit Note, an increase is a Debit Note, and each is itself an e-invoice requiring its own IRN and QR. Amending the ERPNext document without raising the note breaks the audit trail and your return will not reconcile.
+Does the 30-day rule apply to businesses below ₹10 crore?
As of 31 July 2026 the 30-day reporting restriction applies at AATO ₹10 crore and above. Below that you can still report older invoices, but the threshold has only moved downward over time, so building same-day reporting now is the safe default. Confirm the current CBIC/GSTN notification for your period.
Related issues you may also hit
- The GST e-invoicing IRP round-trip — why an IRN fails to generate before the clock even matters.
- GST return filing in ERPNext — where credit notes and missed invoices land in GSTR-1.
- ERPNext blocks backdated stock entries — the same back-dating trap on the stock side.
Closing
The 30-day and 24-hour windows are unforgiving precisely because nothing in your day-to-day flags them until they close. Report at submit, run the ageing report daily, and correct by the clock — cancel inside 24 hours, credit-note after. Do that and both deadlines become invisible background rules instead of the reason a buyer's ITC disappeared on your watch.
Invoices ageing past the reporting window and ITC going missing?
We build the ageing report that surfaces invoices before day 30, set the same-day reporting discipline, and put the cancel-versus-credit-note rules where your finance team will actually follow them.