Section 43B(h): The 45-Day MSME Payment Rule, Decoded

If you run a business and buy from small suppliers, one obscure line in the Income-tax Act can quietly raise your tax bill this year. It is called Section 43B(h), and it ties your right to claim an expense to whether you paid your micro and small vendors on time. Miss the deadline by even a day at year-end, and the deduction slides into the next financial year — pushing up the profit you are taxed on right now.

Introduced by the Finance Act 2023 and live from Assessment Year 2024-25 (financial year 2023-24), the rule was meant to fix a chronic problem: large buyers sitting on payments to tiny suppliers for months, choking their cash flow. Instead of a toothless penalty, the government attached the pain to something every business cares about — its tax deduction. Here is how it actually works, and what to do before 31 March.

What Section 43B(h) actually says

Most business expenses are deductible on an accrual basis: you book the bill, you claim the expense, whether or not you have paid. Section 43B is the exception — it lists payments (taxes, PF, bank interest) that are deductible only when actually paid. The 2023 amendment added clause (h): sums payable to a micro or small enterprise.

The effect is simple but sharp. If, at the close of the financial year, you owe a micro or small supplier beyond the time limit set by the MSMED Act, 2006, that amount is disallowed — added back to your taxable income for the year. You get the deduction back, but only in the year you finally pay.

Crucially, the deduction is deferred, not destroyed. Nobody loses the expense permanently. But the timing shift can be expensive: a ₹40 lakh unpaid bill at year-end becomes ₹40 lakh of extra taxable income, and at roughly 25-30% that is real tax paid a year early.

The 15-day and 45-day clock

The deadline comes from Section 15 of the MSMED Act, and it has two settings:

• No written agreement: payment is due within 15 days of accepting the goods or services.
• Written agreement exists: payment is due by the agreed date — but that date can never exceed 45 days from acceptance, no matter what the contract says.

A contract promising "payment in 90 days" does not override the law; the cap stays 45 days for the purposes of this rule. The clock starts from the date of acceptance (or deemed acceptance) of the supply, not the invoice date — a distinction that trips up many accounts teams.

A practical nuance: the disallowance bites only if the amount is still unpaid at the year-end test and was already overdue. Pay within the window during the year and the expense is allowed normally.

Who is caught — and who is not

This is where most confusion lives. Three points decide whether 43B(h) applies to a transaction.

1. The supplier must be registered. Only vendors with a valid Udyam Registration classified as micro or small trigger the rule. An unregistered small business — however tiny — is outside it.
2. Medium enterprises are excluded. The disallowance covers micro and small only. Buy from a registered medium enterprise and 43B(h) does not apply.
3. The buyer's status is irrelevant. You do not need to be an MSME yourself. A large company, an LLP, even a sole proprietor running a tax audit is caught the moment the supplier is micro or small.

The biggest exception is traders. Wholesalers and retailers can register on Udyam (mainly for priority-sector lending), but the payment-protection benefit of Section 15 was designed for manufacturers and service providers. So dues to a pure trading vendor are generally not disallowed under 43B(h) — a relief for businesses that buy stock from distributors.

After the revised MSME limits effective 1 April 2025, more firms qualify as micro or small, widening the net. The thresholds now read:

• Micro: investment up to ₹2.5 crore and turnover up to ₹10 crore.
• Small: investment up to ₹25 crore and turnover up to ₹100 crore.

The interest sting on top

Disallowance is only half the story. The MSMED Act also entitles a delayed micro/small supplier to interest at three times the RBI bank rate, compounded monthly — a punishing figure designed to make stalling pointless. And under the Income-tax Act, that interest is itself not deductible.

So a chronically late payer faces a double hit: a deferred deduction on the principal, plus non-deductible penal interest if the supplier ever enforces the claim through an MSME Samadhaan facilitation council. Most suppliers stay quiet to protect the relationship — but the legal right sits there.

A simple example

Suppose your firm buys components worth ₹10 lakh from a Udyam-registered small manufacturer on 1 February, with no written agreement. Payment is due by 16 February (15 days). You pay on 20 April instead.

At 31 March, the bill is unpaid and overdue. The ₹10 lakh is added back to your taxable income for that year. When you pay on 20 April, you claim the ₹10 lakh deduction in the next financial year. The expense isn't lost — but you have funded the tax on ₹10 lakh of phantom profit for a full year, purely on a timing mismatch.

What businesses should do now

Compliance is mostly housekeeping, but it has to be deliberate. A practical checklist:

• Collect Udyam numbers. Ask every vendor whether they are registered and in which category, and keep the certificate on file. Without this, your auditor cannot classify dues correctly.
• Flag MSME suppliers in your accounting software. Tag micro/small vendors so the system can throw up an ageing report of overdue MSME bills.
• Run a 31-March sweep. Before year-end, clear every micro/small invoice that is past its 15 or 45-day window. This single discipline prevents most disallowances.
• Fix your payment terms. Where you genuinely need longer credit, renegotiate sourcing — but do not assume a long-dated contract saves you; the 45-day cap overrides it.
• Reconcile with your tax audit. Form 3CD now requires reporting of MSME dues, so mismatches between your books and your return will surface.

Why it matters beyond tax

Section 43B(h) is, at heart, a cash-flow weapon handed to India's smallest firms. For decades, the bargaining power sat with big buyers who could dictate 90- or 120-day terms to vendors with no leverage. By making promptness a condition of the buyer's own tax deduction, the law flips the incentive: paying on time is now cheaper than paying late.

For small suppliers, the takeaway is to get Udyam-registered and ensure your category is recorded correctly — it is what activates the protection. For buyers, the message is blunter: treat micro and small invoices as time-sensitive, build the 15/45-day clock into your payables process, and never let an MSME bill drift across the year-end line. The rule rewards good payment hygiene and quietly taxes bad habits.