Input tax credit explained: Section 16 conditions, GSTR-2B and blocked credits

Input tax credit (ITC) is the GST you paid on business purchases that you can subtract from the GST you collect on sales, so you pay only the difference in cash. To claim it you need a valid invoice that your supplier has reported (so it shows in your GSTR-2B), you must have received the goods or services, and the supplier must have paid the tax. Some credits are blocked outright under Section 17(5), and unpaid suppliers beyond 180 days force a reversal.

What ITC is, in one picture

GST is a value-added tax. Every business in the chain pays tax on its purchases and collects tax on its sales; it remits only the tax on the value it added. The mechanism that makes this work is ITC.

A Surat textile trader buys grey fabric for ₹10,00,000 plus 5% GST (₹50,000) and sells finished sarees for ₹15,00,000 plus 5% GST (₹75,000). He collected ₹75,000, he already paid ₹50,000 to his supplier, so he pays ₹25,000 in cash through GSTR-3B. The ₹50,000 is his input tax credit. Without ITC he would pay ₹75,000 and the tax would cascade at every stage.

ITC is available on inputs (raw materials, trading stock), input services (rent, freight, professional fees, software) and capital goods (machinery, computers, furniture) used in the course or furtherance of business. It is not available on purchases used for personal purposes, for exempt supplies, or on the blocked list.

The Section 16 conditions

Section 16(2) of the CGST Act sets out what must be true before you claim. Each condition has a rule and a practical check.

Two more conditions sit outside 16(2):

• Time limit (Section 16(4)): claim by 30 November following the end of the financial year to which the invoice relates, or the date of filing the annual return, whichever is earlier. An invoice dated 15 March 2026 (FY 2025-26) must be claimed by 30 November 2026.
• No depreciation on the tax component (Section 16(3)): if you claim ITC on a machine, you cannot also claim income tax depreciation on the GST portion. Book the machine at its net-of-GST cost.

Section 16(2)(c) is the condition that catches honest buyers. If your supplier collects GST from you and never pays it, the department can deny your credit. Your protection is to buy from suppliers who file on time, check their filing status on the portal before large orders, and hold back the tax portion of a bill until it appears in your GSTR-2B.

How GSTR-2B matching works month to month

GSTR-2B is a static statement generated on the 14th of every month from the GSTR-1, IFF and GSTR-5/6 returns your suppliers filed up to the 13th. Unlike the older GSTR-2A, it does not change after generation, so the credit shown for a month is the credit you may claim that month.

Since October 2024 the Invoice Management System (IMS) sits in front of GSTR-2B. Invoices your suppliers file appear in IMS where you can accept, reject or keep them pending. Accepted and untouched invoices flow into GSTR-2B; rejected ones do not. Rejecting a wrong invoice (wrong GSTIN, duplicate, not yours) keeps your 2B clean and tells the supplier to fix it. IMS features have changed a few times since launch; confirm the current workflow on the portal.

A practical monthly routine:

1. Record every purchase bill as it arrives, with the supplier GSTIN, invoice number, date, taxable value and tax. This is your purchase register.
2. On the 14th, download GSTR-2B as Excel.
3. Match register to 2B by supplier GSTIN and invoice number. Three buckets result: matched (claim), in register but not in 2B (follow up with the supplier, do not claim yet), in 2B but not in register (find the bill, or reject in IMS if it is not yours).
4. Enter the matched eligible credit in GSTR-3B Table 4(A)(5), reverse ineligible or blocked amounts in 4(B), and report the net in 4(C).

If your claimed ITC in 3B exceeds 2B by more than the permitted margin, the system issues an intimation in Form DRC-01C under Rule 88D asking you to pay or explain within 7 days. Repeated mismatches can block your next GSTR-1.

Blocked credits under Section 17(5)

Some purchases carry GST that you can never claim, even if they are used for business. The main entries:

• Motor vehicles for passengers (up to 13 seats) and the insurance, servicing and repairs on them, unless you are in the business of selling vehicles, transporting passengers or training drivers. Goods vehicles are allowed.
• Vessels and aircraft, with similar exceptions.
• Food and beverages, outdoor catering, beauty treatment, health services, cosmetic surgery, club and fitness memberships, life and health insurance, unless you are obliged by law to provide them to employees or you resell the same category of service.
• Travel benefits to employees on vacation, such as leave travel.
• Works contract services for construction of immovable property (other than plant and machinery), except when you supply works contract services yourself. Renovating your shop premises: blocked. Buying a machine and installing it: allowed.
• Goods or services used for constructing immovable property on your own account, even for business use.
• Goods or services on which tax was paid under the composition scheme.
• Goods or services used for personal consumption.
• Goods lost, stolen, destroyed, written off, or given as gifts or free samples. If you distribute Diwali gifts to customers, reverse the credit on them.
• Tax paid under Sections 74, 129 or 130 (fraud demands, detention, confiscation).

Section 17(1) and 17(2) add proportionate restrictions: credit on inputs used partly for personal or exempt purposes must be reversed in proportion, using the formula in Rules 42 and 43. A Bengaluru cloud kitchen under the 5% restaurant rate cannot claim any ITC at all, because the rate itself is conditional on not taking credit.

The 180-day payment rule and other reversals

The second proviso to Section 16(2) says that if you fail to pay the supplier the value plus tax within 180 days of the invoice date, you must add the ITC to your output liability with interest. Rule 37 spells out the mechanics: reverse in the GSTR-3B for the period in which the 180 days end, pay 18% interest from the date of availment, and re-claim when you actually pay. The rule does not apply where tax is payable under reverse charge, or to supplies without consideration deemed as supply under Schedule I.

For a Kochi electronics shop that bought ₹5,00,000 of stock plus ₹90,000 GST on 1 April 2026 and still has not paid by 28 September 2026 (180 days), the September GSTR-3B must show ₹90,000 in Table 4(B)(2), with interest of roughly ₹90,000 × 18% × 150 ÷ 365 = ₹6,658 for the days since the credit was taken in the April return. Track supplier ageing in the vendor ledger so 180 days never sneaks up.

Other common reversals:

• Credit note from the supplier (price reduction, return): reduce your ITC in the month the credit note appears in 2B.
• Exempt and non-business use (Rules 42 and 43): monthly reversal with an annual true-up by September of the next year.
• Capital goods sold: pay the higher of ITC reduced by 5% per quarter of use, or the tax on the sale value (Section 18(6)).
• Switching to composition or cancellation: pay ITC on stock and capital goods held (Section 18(4)).

How a purchase register feeds GSTR-3B

GSTR-3B Table 4 is where ITC lives. Your purchase register should be organised so the totals fall into these boxes without manual re-sorting.

Every purchase bill therefore needs two flags: whether the credit is eligible (or blocked under 17(5)) and whether it has appeared in 2B. A register with those two flags produces Table 4 in minutes.

A worked example: one month for a Surat textile trader

Ramesh, registered in Gujarat, has the following in August 2026:

Sales: ₹18,00,000 of sarees at 5%. Output tax ₹90,000 (CGST ₹45,000, SGST ₹45,000).

Purchases:

Eligible ITC this month: ₹55,000 + ₹6,000 + ₹7,200 = ₹68,200. The packaging IGST of ₹10,800 is claimed next month when the supplier files. The car and sweets are reported in Table 4(B)(1) as reversed, so the net figure in 4(C) is ₹68,200.

Cash payable: ₹90,000 minus ₹68,200 = ₹21,800, paid through the electronic cash ledger before filing GSTR-3B on the 20th. Had Ramesh claimed the car, his 3B would exceed 2B on eligibility rather than presence, which an audit catches later with 24% interest under Section 50(3) on wrongly availed and utilised credit.

Where to enter the numbers in the return itself is covered in our GSTR-1 and GSTR-3B guide.

Common mistakes

• Claiming on proforma invoices or quotations. Only a tax invoice or debit note qualifies. Ask suppliers for the tax invoice at delivery.
• Wrong GSTIN on the supplier's invoice. If the supplier typed your old GSTIN or a group company's GSTIN, the credit lands in the wrong 2B. Check the invoice on receipt.
• Claiming before the goods arrive. Goods invoiced on 30 June and received on 3 July belong to July's claim.
• Claiming hotel and restaurant bills from other states. Hotel stays outside your state carry another state's SGST that you cannot use, and restaurant bills are blocked anyway.
• Missing the 30 November cut-off. Old invoices found during the audit are lost credits.
• Forgetting reverse charge credit. GST you paid under RCM on freight or legal fees is claimable in the same month you pay it, in Table 4(A)(3). Many small businesses pay RCM and never claim it back.
• Treating cess as GST. Compensation cess credit can be used only against cess liability.
• Not reversing on free samples and gifts. The department checks marketing expenses against ITC reversals.
• Paying suppliers late and forgetting Rule 37. The reversal is due even if the supplier is not chasing you.

How VyaparKit helps

The purchase bill tool records each supplier invoice with an ITC flag, so blocked credits and pending-in-2B bills are separated from eligible ones, and the GST report lists the ITC table in the order GSTR-3B Table 4 needs. The vendor ledger shows how long each supplier has been unpaid, which keeps you clear of the 180-day reversal. On the sales side, the GST invoice tool captures the customer's GSTIN correctly so your invoices land in their 2B. VyaparKit does not file GSTR-3B or fetch GSTR-2B; download 2B from the portal and match it to your purchase register.

Next steps

• Set up a purchase register with columns for supplier GSTIN, invoice number, date, taxable value, tax, eligibility flag and 2B status.
• Download GSTR-2B on the 14th of every month and match it before you prepare 3B.
• Mark every 17(5) item (vehicles, food, gifts, construction) as blocked at the time of entry.
• Run a supplier ageing report monthly and pay anything approaching 180 days.
• Before 30 November, sweep the previous financial year for any credit not yet claimed.