Think of Input Tax Credit (ITC) as the GST you've already paid on your purchases — Section 16 tells you when you're allowed to use that money to reduce your GST liability. It's one of the most exam-important sections in all of GST, and getting the conditions wrong is a very common reason students lose marks.
The basic rule under Section 16(1) is simple: if you're a registered person and you buy goods or services for your business, you can claim the GST paid on those purchases. That credit lands in your Electronic Credit Ledger — think of it as a GST wallet. But Section 16(2) says you can't touch that credit unless all four conditions are met simultaneously: (a) you hold a valid tax invoice or debit note from a GST-registered supplier; (b) you have actually received the goods or services (for goods delivered in lots, you can only claim ITC after the last instalment arrives); (c) the supplier has actually paid the tax to the government; and (d) you have filed your own GST return under Section 39. Miss even one of these four, and your ITC claim is invalid.
Two extra traps to watch for: First, the 180-day payment rule — if you haven't paid your supplier (invoice value + tax) within 180 days of the invoice date, the ITC you already claimed gets reversed and added back to your output tax, plus interest. Once you pay, you can reclaim it. Second, the time limit under Section 16(4) — you must claim ITC by the earlier of: (i) the due date of the September return of the next financial year, or (ii) the date of filing the annual return. For an invoice dated in FY 2024-25, the deadline is 20th October 2025 (due date for September 2025 GSTR-3B). Miss this, and the ITC is gone forever. Also, Section 16(3): if you've claimed depreciation on the GST component of a capital good under the Income Tax Act, you cannot also claim ITC on that GST — no double benefit.
📊 Worked example
Example 1 — 180-Day Rule Reversal
Rajesh & Co. Pvt. Ltd. receives an invoice from a supplier on 1 April 2024 for goods worth ₹5,00,000 + GST @ 18% = ₹90,000. They claim ITC of ₹90,000 in April 2024.
By 29 September 2024 (180 days from invoice), they have only paid ₹2,00,000 to the supplier — not the full amount.
Working:
- Total invoice value (incl. tax) = ₹5,90,000
- Paid = ₹2,00,000
- Unpaid = ₹3,90,000
- ITC attributable to unpaid portion = ₹90,000 × (₹3,90,000 ÷ ₹5,90,000) = ₹59,491 (approx.)
This ₹59,491 must be added back to output tax liability in the October 2024 return, along with applicable interest. When Rajesh & Co. eventually pays the supplier in full, they can re-avail the ₹59,491 ITC.
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Example 2 — Time Limit Under Section 16(4)
Ms. Iyer's firm receives an invoice dated 15 March 2025 (FY 2024-25) for services worth ₹2,00,000 + GST 18% = ₹36,000.
She forgets to claim ITC and tries to do so in November 2025.
Working:
- Invoice FY = 2024-25
- Deadline = earlier of: due date of September 2025 GSTR-3B (i.e., 20 October 2025) OR date of annual return filing
- Ms. Iyer is claiming in November 2025 — past the deadline
Final Answer: ITC of ₹36,000 is permanently lost. No extension is available under normal circumstances.
⚠️ Common exam mistakes
- Students think all four conditions under 16(2) are independent — they are not. All four must be satisfied simultaneously. Don't assume that just because you have the invoice, you can claim ITC; if your return isn't filed, you can't.
- Confusing '180 days from invoice date' with '180 days from payment due date' — the 180-day clock starts from the date of invoice, not the credit period or due date agreed with the supplier.
- Thinking ITC on capital goods can be claimed AND depreciation taken on the full cost — Section 16(3) prohibits this. If you claim depreciation on the GST amount under Income Tax, you forfeit the ITC. Pick one.
- Missing the Section 16(4) deadline — students often think the deadline is 31 March of the next year. It is actually the due date of the September return of the following FY (typically 20 October), or the annual return date, whichever is earlier. One month difference can cost you the entire ITC.
- Claiming ITC on goods received in instalments before the last lot arrives — Section 16(2)(b) proviso says ITC is available only after the last instalment or lot is received. Don't book ITC parcel-by-parcel.
📖 Bare Act text — Section 16, CGST Act 2017
(click to expand)
(1) Every registered person shall, subject to such conditions and restrictions as may be prescribed and in the manner specified in section 49, be entitled to take credit of input tax charged on any supply of goods or services or both to him which are used or intended to be used in the course or furtherance of his business and the said amount shall be credited to the electronic credit ledger of such person.
(2) Notwithstanding anything contained in this section, no registered person shall be entitled to the credit of any input tax in respect of any supply of goods or services or both to him unless,––
(a) he is in possession of a tax invoice or debit note issued by a supplier registered under this Act, or such other tax paying documents as may be prescribed;
(b) he has received the goods or services or both.
[Explanation.— For the purposes of this clause, it shall be deemed that the registered person has received the goods or, as the case may be, services––
(i) where the goods are delivered by the supplier to a recipient or any other person on the direction of such registered person, whether acting as an agent or otherwise, before or during movement of goods, either by way of transfer of documents of title to goods or otherwise;
(ii) where the services are provided by the supplier to any person on the direction of and on account of such registered person;]
(c) subject to the provisions of section 41, the tax charged in respect of such supply has been actually paid to the Government, either in cash or through utilisation of input tax credit admissible in respect of the said supply; and
(d) he has furnished the return under section 39:
Provided that where the goods against an invoice are received in lots or instalments, the registered person shall be entitled to take credit upon receipt of the last lot or instalment:
Provided further that where a recipient fails to pay to the supplier of goods or services or both, other than the supplies on which tax is payable on reverse charge basis, the amount towards the value of supply along with tax payable thereon within a period of one hundred and eighty days from the date of issue of invoice by the supplier, an amount equal to the input tax credit availed by the recipient shall be added to his output tax liability, along with interest thereon, in such manner as may be prescribed:
Provided also that the recipient shall be entitled to avail of the credit of input tax on payment made by him of the amount towards the value of supply of goods or services or both along with tax payable thereon.
(3) Where the registered person has claimed depreciation on the tax component of the cost of capital goods and plant and machinery under the provisions of the Income-tax Act, 1961, the input tax credit on the said tax component shall not be allowed.
(4) A registered person shall not be entitled to take input tax credit in respect of any invoice or debit note for supply of goods or services or both after the due date of furnishing of the return under section 39 for the month of September following the end of financial year to which such invoice or invoice relating to such debit note pertains or furnishing of the relevant annual return, whichever is earlier.
[Provided that the registered person shall be entitled to take input tax credit after the due date of furnishing of the return under section 39 for the month of September, 2018 till the due date of furnishing of the return under the said section for the month of March, 2019 in respect of any invoice or invoice relating to such debit note for supply of goods or services or both made during the financial year 2017-18, the details of which have been uploaded by the supplier under sub-section (1) of section 37 till the due date for furnishing the details under sub-section (1) of said section for the month of March, 2019.]
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