The 180-day payment rule in one clear picture
If a registered person has availed ITC on an inward supply and fails to pay the supplier the value of the supply together with the tax within 180 days from the invoice date, the unpaid portion of the ITC becomes subject to reversal under Section 16(2) read with Rule 37.
Check ITC eligibility
Track invoice
Monitor payment
Proportionate reversal
Re-avail eligible credit
Think of this as a vendor-payment control attached to ITC. A vendor ageing report alone is not enough: the GST team needs invoice-level ITC, payment and reversal information.
Legal framework: Section 16(2) + Rule 37
Contains the 180-day payment condition attached to ITC.
Provides the operational mechanism for reversal and later re-availment.
The reversal is reported through the ITC reversal mechanism.
Rule 37 was materially amended from 1 October 2022 and subsequently clarified so that the mechanism expressly addresses supplies that are wholly or partly unpaid and proportionate reversal.
When does the 180-day period start?
The statutory trigger is linked to 180 days from the date of issue of the supplier's invoice. The best practice is therefore to calculate the date invoice-by-invoice.
| Situation | Practical decision |
|---|---|
| Fully paid within 180 days | No Rule 37 reversal for that payment condition. |
| Partly paid within 180 days | Assess the unpaid proportion and corresponding ITC. |
| Still unpaid after 180 days | Calculate reversal and applicable interest. |
| Paid after reversal | Verify payment and re-avail the eligible reversed ITC. |
How much ITC should be reversed?
The current Rule 37 approach is proportionate where the consideration is partly unpaid. Do not blindly reverse 100% merely because an invoice crossed 180 days.
The payment condition concerns the value of supply together with the tax payable. Your working should therefore connect the invoice gross amount, payments and unpaid amount rather than using only the taxable value.
Example: completely unpaid
| Particular | Amount |
|---|---|
| Taxable value | ₹10,00,000 |
| GST @ 18% | ₹1,80,000 |
| Gross invoice | ₹11,80,000 |
| Eligible ITC availed | ₹1,80,000 |
| Paid within 180 days | ₹0 |
| ITC requiring reversal | ₹1,80,000 |
Example: 30% remains unpaid
For the same ₹11,80,000 invoice, assume ₹8,26,000 is paid within 180 days and ₹3,54,000 remains unpaid. The unpaid portion is 30%.
The remaining ₹1,26,000 is not automatically reversed merely because the invoice was not completely settled, subject to correct payment allocation and all other ITC conditions.
Partial payment: the area where businesses often go wrong
Businesses with running accounts, milestone payments, retention money and multiple payment entries need invoice-level mapping. Comparing only total vendor outstanding with total ITC can give the wrong result.
Works contractor example
| Particular | Amount |
|---|---|
| Taxable value | ₹20,00,000 |
| GST | ₹3,60,000 |
| Gross invoice | ₹23,60,000 |
| ITC availed | ₹3,60,000 |
| Paid within 180 days | ₹17,70,000 |
| Unpaid | ₹5,90,000 = 25% |
| ITC reversal | ₹90,000 |
Multiple payments against one invoice
Maintain invoice number, invoice date, gross value, each payment date, cumulative amount paid, unpaid amount, 180-day date, reversal and reclaim. This creates an audit trail that can be defended later.
Interest: do not use a simplistic “18% × 180 days” formula
Rule 37 requires the applicable interest under Section 50 along with the reversal. But interest should not be calculated merely by taking 18% for 180 days in every case.
The statutory interest framework for wrongly availed and utilised ITC considers the manner in which the credit was utilised and the computation prescribed under the law. Therefore, a proper working should establish:
- date of original ITC availment;
- amount subject to reversal;
- whether and when the relevant credit was utilised;
- date of reversal/payment; and
- the applicable rate and computation mechanism.
This distinction is important because many online articles present a single formula without analysing utilisation.
Does the 180-day rule apply to every purchase?
No. First identify whether the transaction falls within the Rule 37 mechanism.
Rule 37 specifically excludes inward supplies on which tax is payable under reverse charge. RCM ITC should be controlled separately.
Rule 37 contains a deeming provision treating specified Schedule I supplies without consideration as paid for this purpose.
The rule contains a specific deeming treatment for relevant amounts added under Section 15(2)(b).
Payment within 180 days does not make otherwise ineligible ITC eligible. Section 17(5), Section 16(4) and other conditions still need testing.
What happens when the supplier is paid later?
₹1,80,000
₹54,000 reversal
Balance settled
₹54,000 if eligible
Rule 37 permits re-availment after the relevant payment is subsequently made. Keep evidence of the payment and link it to the invoice and earlier reversal.
How should Accounts Payable, GST and ERP work together?
The strongest control combines vendor ageing + invoice register + ITC register + payment data + reversal/reclaim register.
| Control field | Purpose |
|---|---|
| Supplier GSTIN / name | Correct vendor identification. |
| Invoice number/date | Core invoice and 180-day trigger. |
| Gross invoice value | Payment proportion. |
| Eligible ITC | Maximum credit exposed. |
| Payment dates and amounts | Determine settlement within 180 days. |
| Unpaid amount | Calculate proportionate reversal. |
| 180-day date | Compliance alert. |
| Reversal month/amount | GSTR-3B and ledger control. |
| Later payment date | Reclaim trigger. |
| Reclaim amount/date | Prevents lost or duplicate credit. |
0–150 days
Monitor normally.
151–180 days
Escalate to AP/procurement.
Over 180 days
Perform Rule 37 review.
Practical decision cases
Invoice paid on day 175
Decision: no Rule 37 reversal merely because the payment was close to 180 days. Keep payment evidence and continue other ITC checks.
Invoice paid on day 181
Decision: the 180-day condition was not met. If Rule 37 applies, calculate the proportionate reversal and applicable interest. Later payment permits re-availment of eligible reversed credit.
50% of invoice remains unpaid
Decision: do not automatically reverse 100%. Determine the ITC attributable to the unpaid proportion.
Supplier is under RCM
Decision: do not apply the normal Rule 37 vendor-payment test mechanically; RCM supplies are specifically excluded from Rule 37.
Invoice fully paid but ITC is blocked under Section 17(5)
Decision: payment does not cure blocked ITC. Eligibility must be tested independently.
Old vendor balance but invoices are settled
Decision: do not rely on vendor-level ageing alone. Reconcile invoice-level settlement.
Common mistakes
Wrong starting point. Test the invoice and ITC.
Current Rule 37 requires proportionate treatment.
The condition concerns value plus tax.
Temporary reversals need a reclaim register.
Analyse utilisation and statutory computation.
Different triggers, different controls.
The 180-day test needs AP/payment data too.
Payment, reversal and reclaim must be traceable.
Monthly 180-day ITC checklist
- Prepare the ITC invoice register.
- Calculate the 180-day date invoice-wise.
- Map payments from bank/AP records to invoices.
- Identify partly and wholly unpaid invoices.
- Separate RCM and other transactions requiring different treatment.
- Calculate proportionate reversal.
- Review applicable interest and computation.
- Report reversal in the appropriate GSTR-3B ITC reversal field.
- Create a temporary reversal register.
- Every month match later payments against the reversal register.
- Re-avail eligible reversed ITC after payment.
- Reconcile reversal/reclaim with GSTR-3B and the general ledger.
Frequently asked questions
Does ITC permanently disappear after 180 days?
No. The credit can generally be re-availed after the relevant supplier payment, subject to the underlying ITC remaining eligible.
Is the 180-day period counted from invoice date?
Yes. The condition is linked to 180 days from the date of issue of the supplier's invoice.
What if only part of the invoice is unpaid?
The current Rule 37 mechanism provides for proportionate reversal corresponding to the unpaid consideration.
Does Rule 37 apply to RCM?
Rule 37 specifically excludes inward supplies on which tax is payable under reverse charge.
Can reversed ITC be reclaimed after payment?
Yes, Rule 37 provides for re-availment after subsequent payment to the supplier, subject to eligibility.
Is Rule 37 the same as Rule 37A?
No. Rule 37 concerns the recipient's non-payment; Rule 37A concerns a different supplier-compliance trigger.
Does paying within 180 days guarantee ITC?
No. Other ITC eligibility conditions and restrictions continue to apply.
Should this be checked only at year end?
No. Monthly monitoring is much safer because invoices cross 180 days throughout the year and later reclaims also need tracking.
More GST Resources for Your Day-to-Day Work
You have understood the 180-day payment rule. Now connect it with the other GST checks that an accounts and tax team performs every month.
180 days is a payment control, not just a GST calculation.
The safest workflow is: