Input tax credit is the engine of GST — it is what stops tax from stacking on tax as goods and services move through the chain. But two things quietly erode the credit that businesses assume is theirs: a hard list of expenses on which credit is simply never allowed (Section 17(5), the “blocked credits”), and a timing rule that claws back credit you have already taken if you don’t pay your supplier within 180 days.
Both cost real money, and both show up in departmental reconciliations long after the fact. This article sets out the blocked-credit list that businesses most often get wrong, then walks through the 180-day reversal trap with the exact mechanics — when it bites, how much interest, and how to get the credit back.
First, the four conditions to claim ITC at all
Before worrying about what is blocked, remember that Section 16(2) lets you claim ITC only when all of these are satisfied: you hold a valid tax invoice or debit note; the invoice appears in your auto-drafted GSTR-2B (Section 16(2)(aa)); you have actually received the goods or services; the tax has actually been paid to the government by the supplier; and you have furnished your return. On top of that, Section 16(4) sets an outer time limit — ITC for a financial year must be claimed by 30 November of the following year (or the date of filing the annual return, if earlier). Miss that window and the credit lapses permanently. Only once these gates are cleared do the Section 17(5) and 180-day rules come into play.
Section 17(5): credits that are blocked no matter what
Section 17(5) lists specific inward supplies on which ITC is denied even if they are used for business. These are the ones businesses most frequently claim by mistake:
| Clause | Blocked credit | Key exception |
|---|---|---|
| (a) | Motor vehicles for transport of persons with approved seating capacity of 13 or fewer (including driver) | Allowed if used for further supply of vehicles, transport of passengers, driving training, or if you are the manufacturer |
| (aa) | Vessels and aircraft | Same business-use exceptions as above |
| (ab) | Insurance, servicing, repairs and maintenance of the above blocked vehicles/vessels/aircraft | Follows the vehicle: allowed only where the vehicle itself is eligible |
| (b) | Food and beverages, outdoor catering, health services, cosmetic/plastic surgery, club and fitness membership, life and health insurance, rent-a-cab | Allowed where it is an inward leg of an outward taxable supply, or where the employer is obligated by law to provide it to employees |
| (c) & (d) | Works contract services and goods/services used for construction of immovable property on own account | Allowed for plant and machinery, and where it is an input to a further works-contract supply |
| (e) | Inward supplies of a person paying tax under the composition scheme | — |
| (g) | Goods/services used for personal consumption | Business-use portion remains eligible |
| (h) | Goods lost, stolen, destroyed, written off, or given as gifts or free samples | — |
| (fa) | Goods/services used for CSR activities under the Companies Act | Blocked with effect from 1 October 2023 |
The three that catch businesses out most often are the staff-welfare spends under clause (b) — the office party, the team lunch, the gym membership — on which credit is denied unless the law obliges you to provide the benefit; the construction clause (c)/(d), where the fit-out of your own office is blocked but genuine plant and machinery is not; and clause (h), where goods written off or handed out as free samples must have their credit reversed. Note the December 2024 amendment which aligned clause (d) to read “plant and machinery,” clarifying the long-running construction dispute.
If you are weighing a big-ticket purchase and want to know whether the GST on it is a real cost or a recoverable credit, model it first with our GST Calculator or run the specifics past our Ask a CA – GST desk before you commit.
The 180-day trap: pay your supplier, or lose the credit
This is the rule that surprises otherwise careful businesses. Under the second proviso to Section 16(2), read with Rule 37, if you claim ITC on an invoice but do not pay the supplier the value of the supply and the tax on it within 180 days from the date of the invoice, you must reverse that credit. The trigger is non-payment, not a defective invoice — and it applies even where the supplier has correctly paid the tax to the government.
How the reversal works
When 180 days lapse without payment, the ITC already availed is added to your output tax liability in the GSTR-3B of the period in which the 180 days expire. Since the October 2022 amendment removed the old GSTR-2 route, the reversal is now made directly in GSTR-3B (reported through Table 4B). You also pay interest under Section 50 at 18% on the reversed amount, computed from the date you originally availed the credit up to the date of reversal.
Partial payment means partial reversal
If you have paid part of the invoice, you reverse only the ITC proportionate to the unpaid portion. You do not lose credit on the amount you have actually paid.
The good news: you get it back when you pay
The reversal is not permanent. Under the third proviso to Section 16(2), once you make the payment to the supplier, you can re-avail the reversed credit — and, importantly, the Section 16(4) time limit does not apply to this re-availment. So a credit reversed for non-payment can be reclaimed whenever the payment is eventually made, even in a later year.
A worked example
Apex Traders receives an invoice dated 5 April 2026 for Rs. 5,00,000 plus GST of Rs. 90,000 (18%), and claims the full Rs. 90,000 as ITC in its April GSTR-3B. A cash crunch means the supplier remains unpaid.
| Event | Date | Consequence |
|---|---|---|
| ITC availed on invoice | Apr 2026 GSTR-3B | Rs. 90,000 credit taken |
| 180 days from invoice date | ~2 Oct 2026 | Deadline to pay supplier the Rs. 5,90,000 |
| Still unpaid — reversal due | Oct 2026 GSTR-3B | Rs. 90,000 added back to output tax; interest at 18% from Apr availment to reversal |
| If Rs. 2,95,000 (half) had been paid | — | Only Rs. 45,000 reversed (proportionate to unpaid half) |
| Supplier paid in full later | e.g. Feb 2027 | Re-avail the Rs. 90,000 — no 16(4) time bar on re-availment |
Assuming the credit is reversed roughly six months after it was availed, the 18% interest on Rs. 90,000 works out to about Rs. 8,100 — a pure cost of delay, on top of the cash-flow hit of temporarily losing the credit. The lesson for accounts-payable teams is simple: track invoice-payment against a 180-day clock, not just against vendor reminders.
Blocked credit vs reversed credit — don’t confuse them
These two are often lumped together but behave very differently. A Section 17(5) blocked credit is never available — there is nothing to re-avail, and taking it in the first place is an error to be corrected with interest. A 180-day reversal is a temporary loss of an otherwise-valid credit that comes back once you pay. Getting the classification right matters, because it decides whether you are looking at a permanent cost or a timing cost.
Key takeaways
- ITC is available only when all of Section 16(2)’s conditions are met — valid invoice, appearing in GSTR-2B, goods/services received, tax paid to government, return filed — and it must be claimed by 30 November of the following year (Section 16(4)).
- Section 17(5) permanently blocks credit on passenger motor vehicles (≤13 seats), staff food/health/club benefits, own-account construction, personal-use goods, free samples/gifts, and (from Oct 2023) CSR spends — each with narrow exceptions.
- The 180-day rule (second proviso to Section 16(2), Rule 37) forces reversal of ITC if you don’t pay the supplier within 180 days of the invoice date.
- Reversal is done in GSTR-3B with 18% interest under Section 50 from the date of availment; partial payment means proportionate reversal.
- Reversed credit can be re-availed once payment is made, free of the Section 16(4) time limit.
- A blocked credit is a permanent cost; a 180-day reversal is only a timing cost — treat them differently.
Frequently Asked Questions
Can I claim ITC on a car bought for my business?
Generally no. Section 17(5)(a) blocks credit on motor vehicles for transport of persons with an approved seating capacity of 13 or fewer. Credit is allowed only if you are in the business of supplying such vehicles, providing passenger transport, running a driving school, or you are the manufacturer. A commercial goods-carriage vehicle is outside this block and its ITC is available.
The supplier has already paid GST to the government — do I still have to reverse ITC if I haven’t paid them?
Yes. The 180-day rule under the second proviso to Section 16(2) is triggered by your non-payment to the supplier, independent of whether the supplier has deposited the tax. If you have not paid the value of the supply plus tax within 180 days of the invoice date, the credit must be reversed — and re-availed later when you pay.
How much interest do I pay on a 180-day reversal?
Interest is charged under Section 50 at 18% per annum on the reversed ITC, computed from the date you originally availed the credit until the date of reversal. This is a real cost, so tracking supplier payments against the 180-day clock is worth the effort. Our GST Calculator can help you quantify the tax and interest at stake.
Is ITC on office renovation or construction available?
No, where it is on your own account. Section 17(5)(c)/(d) blocks credit on works contract services and goods/services used for construction of immovable property for your own use. The important exception is plant and machinery, on which credit remains available. Distinguishing a civil fit-out from eligible plant and machinery is a common grey area — worth confirming via Ask a CA – GST.
I reversed ITC for non-payment last year. Can I still get it back?
Yes. Under the third proviso to Section 16(2), once you pay the supplier you may re-avail the reversed credit, and the Section 16(4) time limit does not apply to this re-availment. So a credit reversed in one financial year can be reclaimed in a later year when the payment is finally made.