A 25-year economist designed GST to remove cascading. Tax on tax. The mechanism: every link in the supply chain pays GST only on its own value addition, claiming credit for GST already paid upstream. Break the chain (missed vendor filing, wrong GSTIN on invoice, payment outside 180 days) and input credit is denied. Which unravels the economy of a transaction. One major B2B retailer in 2023 had Rs. 40 crore of input credit blocked because 8% of its vendors missed GSTR-1 filings; reconciliation took 6 months.
By the end, you will know the 5 conditions that must hold for input credit to be valid, the GSTR-2B reconciliation that catches errors before filing, and the 180-day payment rule that triggers reversals.
The 5 conditions (section 16)
Tax invoice or debit note held by recipient. Must have GSTIN, HSN/SAC code, tax rate, tax amount separately shown.
Goods / services received by recipient (proof of delivery or service acceptance).
Tax actually paid by supplier (verified via GSTR-1 to auto-population in GSTR-2B).
Return (GSTR-3B) filed by recipient for the relevant month.
Payment to supplier within 180 days of invoice. Non-payment triggers reversal of credit with interest.
The 5 conditions must hold CONCURRENTLY. Missing any one = credit denied for that invoice. The most common failure: (3) supplier did not file GSTR-1 or filed it incorrectly, so your GSTR-2B does not show the invoice. This is where vendor management becomes an operational requirement. Vendors who do not file on time become effectively "more expensive" because their invoices drag input-credit cash flow.
GSTR-2B. The input-credit ledger
From October 2022, the government made GSTR-2B (auto-populated from suppliers' GSTR-1) the SOLE BASIS for input credit. Pre-2022, GSTR-2A was informational; buyers could claim credit on invoices not yet appearing in 2A. Post-2022, 2B is definitive. No 2B entry, no credit. This forces buyers to demand filing compliance from vendors, creating market pressure on vendors to file on time.
Reconciliation workflow: month-end, download GSTR-2B, cross-check with purchase ledger. Missing invoices to escalate with vendor, demand GSTR-1 filing. Once 2B has the invoice, claim credit in next GSTR-3B. Large taxpayers do this via GST reconciliation software (ClearTax GST, Tally ERP, MARG); small freelancers do it via spreadsheet. Either way, the discipline is the same.
The 180-day payment rule
If you claim input credit but do not pay the supplier within 180 days of invoice date, input credit reverses under section 16(2) proviso. Interest at 18% p.a. from the credit-claim date applies. Credit becomes re-claimable once payment is finally made. But the interest reversal stays. This is designed to prevent companies from claiming input credit indefinitely on unpaid invoices; it forces actual payment within a reasonable window.
Practical impact: businesses with long payment cycles (60-90 day credit) can occasionally brush up against 180 days; businesses with contested invoices or ongoing disputes need to track the 180-day clock carefully. Automation helps. ERP systems flag approaching 180-day deadlines automatically.
180-day payment rule
Claim input credit but do not pay supplier within 180 days = credit reverses with interest. Re-claimable once payment is made but is a cash-flow drag. Set up ERP flags for approaching deadlines.
180-day payment rule
Input credit reverses if supplier not paid within 180 days. Interest at 18% p.a. applies. Re-claimable post-payment but cash-flow impact is real.
Vendor filing compliance affects cash flow
Supplier fails to file GSTR-1 = your 2B missing that invoice = no input credit. Creates market pressure on vendors to file on time; non-compliant vendors become effectively "more expensive".
GSTR-2A vs 2B. The 2022 transition
Pre-Oct 2022: GSTR-2A (informational) was the reference. Post-Oct 2022: GSTR-2B is definitive. Old CAs quoting 2A-based claim logic are outdated.
Key Takeaways
Input credit = GST paid on business inputs, offset against GST collected.
Five conditions (section 16) must all hold concurrently.
GSTR-2B is the sole credit-eligible basis from October 2022.
Supplier filing compliance directly affects your cash flow.
Pay suppliers within 180 days or lose the credit temporarily.
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