One invoice at a time: supplier class, the 15/45-day MSMED window from acceptance, and the year-end test — with the verdict written the way it goes into the working paper.
This checker runs one invoice; the audit runs a register. The companion guide covers the six-step approach — building the supplier-class register from Udyam certificates, the trader carve-out reasoning, the year-end three-way split, and the MSMED Sec 16 interest that is disallowed forever — read the 43B(h) audit guide.
Three gates in sequence. First, the supplier: only Udyam-registered micro and small enterprises count — medium enterprises are outside, and purchases from traders are generally outside because the MSMED supplier definition covers manufacturers and service providers.
Second, the window: MSMED Sec 15 requires payment by the agreed date (an agreement cannot stretch beyond 45 days from acceptance) or within 15 days where no written agreement exists. The clock starts at acceptance of the goods or services.
Third, the year-end status: paid within the window, the deduction stays on accrual; window still open at year end and honoured, it also stays; window expired with the amount unpaid at year end, the deduction is disallowed under 43B(h) and returns only in the year of actual payment — the proviso that saves other 43B items by return-date payment expressly does not apply to clause (h).
Goods accepted from a small enterprise on 20 February 2026, no written agreement (15-day window), invoice ₹5,00,000, unpaid on 31 March 2026 and paid on 15 April 2026.
