The 15 September 2026 deadline is the second advance-tax checkpoint for FY 2026–27. By that date, cumulative advance tax should generally reach at least 45% of the estimated annual advance-tax liability. For businesses, professionals, investors, and taxpayers with irregular income, the right number cannot be produced by simply dividing last year’s tax by four. It should be built from current books, a realistic forecast, eligible tax credits, and documented assumptions.
A reliable September estimate starts with actual taxable income and expenses, supported by cash-flow information. This approach helps reduce avoidable interest exposure and gives you a clear record of how the estimate was prepared.
1. Why the September Instalment Trips People Up
By 15 September, cumulative advance tax should generally reach at least 45% of the estimated annual liability, compared with at least 15% by 15 June. September is more difficult because many businesses do not yet have complete visibility through March, and income rarely arrives evenly across the year.
A large invoice, a delayed receivable, a property transaction, or a seasonal change in business can materially alter the annual estimate. The calculation should therefore reflect current facts rather than a simple quarterly average.
2. Start with Your Books, Supported by Cash Flow
Dividing last year’s total tax by four is an easy shortcut, but it can be unreliable if the business has grown, contracted, lost a major client, or incurred unusual expenses.
Start with the books: review taxable income and deductible expenditure recorded from April through August. Then use bank movements and the cash-flow forecast as cross-checks. Adjust the estimate for accruals, receivables, advances, non-cash deductions, disallowances, depreciation, and other tax-specific items. Bank receipts alone are not a substitute for the taxable-income computation where an accrual-based method applies.
For the balance of the year, use signed contracts, pending invoices, known seasonal patterns, expected expenses, and other reasonable assumptions. Record the basis for each significant assumption.
3. Where These Estimates Usually Go Wrong
Common omissions and errors in September advance-tax working papers include:
- Accrued revenue or other taxable income omitted because it has not yet been received in cash
- Bonus, commission, interest, dividend, or other income missed in the projection
- TDS credits assumed without reconciling them with Form 26AS
- AIS information not reviewed for possible mismatches or additional income indicators
- Expenses estimated too conservatively, or expenses included without checking their tax allowability
- Depreciation, brought-forward losses, or other permitted deductions forgotten in the rush
- Capital gains, ESOP vesting, or other lumpy income excluded from the estimate
Several small errors can either cause an unnecessary cash outflow or create a shortfall that may lead to interest under the applicable advance-tax provisions.
4. Building an Estimate You Can Actually Defend
“Defensible” does not mean perfect. It means you can explain how the number was calculated and support the material assumptions if the estimate is later reviewed. Keep a simple working file containing:
- Actual income and expenses recorded from April through August
- The assumptions supporting the September-to-March projection, written in plain language
- Large one-time transactions included or excluded, with the reason documented
- The tax computation after applicable deductions, disallowances, and depreciation
- The TDS and other tax-credit reconciliation using Form 26AS, together with a review of AIS
- A record of tax already paid and the cumulative amount required by 15 September
If the estimate later changes because a client delays payment, a contract is cancelled, or another reasonable assumption changes, this record shows that the calculation was prepared in good faith and updated as new information became available.
5. Handling Capital Gains and One-Off Income
Property sales, mutual-fund redemptions, securities transactions, and ESOP vesting do not necessarily occur evenly across the year. They should be reviewed when the income accrues and should not be forced into an artificial quarterly pattern.
Capital gains and other specified one-off income should generally be included in the next remaining advance-tax instalment after the income accrues. The law also provides exceptions from instalment-interest consequences for certain specified income, subject to payment of the related tax through the remaining instalments immediately due after accrual. The exact treatment depends on the transaction, the timing, and the applicable provisions, so a transaction-specific review is advisable for substantial or complex events.
6. What It Costs You If the Estimate Is Off
Section 424 concerns failure to pay advance tax or payment below the statutory 90% threshold, while Section 425 concerns deferment or short payment of specified advance-tax instalments. The applicable interest period, amount, and statutory exceptions depend on the final assessed tax, payment history, income type, and other facts.
The amount may be material where the tax liability is substantial or a shortfall continues across instalments. A revised estimate should be prepared before the next due date rather than waiting until the end of the financial year.
7. A September Advance-Tax Checklist
- Update the books through 31 August.
- Estimate full-year taxable income, not only cash receipts.
- Include business income, salary, interest, dividends, capital gains, ESOP income, and other one-off income where applicable.
- Review eligible expenses, depreciation, brought-forward losses, disallowances, and the applicable tax regime.
- Reconcile TDS and other tax credits with Form 26AS and review AIS for mismatches.
- Reduce tax already paid and calculate the cumulative amount required by 15 September.
- Document significant assumptions and unusual transactions.
- Revisit the estimate before 15 December and 15 March.
8. How JD Shah Associates Can Help
JD Shah Associates helps businesses, professionals, and NRIs review advance-tax estimates, reconcile TDS and AIS data, assess capital gains and other one-off income, and document the assumptions supporting each instalment. The team also provides direct-tax advisory and compliance support from its Borivali, Mumbai office.
Disclaimer: This article is for general information only and is not tax, legal, or investment advice. Advance-tax treatment depends on the taxpayer’s facts, accounting method, tax regime, income type, and applicable law. Please obtain professional advice before making a payment.
