Most corporate tax problems in Singapore aren’t filing late, IRAS sends enough reminders that outright missed deadlines are rare. The real mistakes are quieter: a filing that goes in on time but has errors that either cost the company money it didn’t need to lose, or draw a query that takes weeks to resolve.
Missing the Estimated Chargeable Income (ECI) deadline. Most companies have to file ECI within three months of their financial year end, separately from the actual tax return, this is easy to overlook because it feels like a preliminary step rather than a real filing, but it carries its own deadline and its own consequences for being late. Some companies qualify for exemption from ECI filing (based on revenue and nil estimated chargeable income thresholds), but that exemption has to actually apply to your situation, it isn’t automatic just because the number feels small.
Confusing accounting profit with chargeable income. These are not the same number, and treating them as interchangeable is one of the most common real errors. Chargeable income starts from accounting profit but requires adding back non-deductible expenses (certain entertainment costs, private motor vehicle expenses, fines) and adjusting for non-taxable income and capital items. A tax computation that just restates the accounting profit without these adjustments is technically incomplete, even if nobody notices until IRAS asks a question.
Getting capital allowances wrong in either direction. Under-claiming allowances on qualifying fixed assets means paying more tax than necessary. Over-claiming or claiming allowances on assets that don’t actually qualify, creates the kind of discrepancy that draws a query. Unabsorbed capital allowances and losses can usually be carried forward to offset future income, but carrying them forward correctly depends on meeting a shareholding continuity test; a change in major shareholders between the loss year and the year it’s used can break that carry-forward without anyone realizing until it’s examined.
Not confirming entitlement to current rebates and exemptions. The Start-Up Tax Exemption scheme and the current Corporate Income Tax Rebate (set at 40% for Year of Assessment 2026, capped at S$30,000, per this year’s Budget) both have specific eligibility conditions, they’re not automatically applied to every company just because the scheme exists. Worth confirming current rates and caps directly with IRAS or your tax advisor before relying on a specific figure, since these numbers are set annually and can change.
What actually prevents these. Reconciling the tax computation against the financial statements line by line rather than treating the tax return as a repackaging of the accounting figures, and checking shareholding continuity before assuming carried-forward losses or allowances are still available.