Company Tax Filing Singapore: ECI Explained, the Deadline, the Waiver and How It Differs from Form C-S

Most founders assume company tax filing Singapore-style is one form a year, due in November. It is actually two. The first, Estimated Chargeable Income (ECI), lands within three months of your financial year end, often before your accounts are closed, and it is the filing new directors most often forget. If your year ended on 30 September 2026, your ECI filing deadline is 31 December 2026, and filing by 26 October 2026 gets you the longest instalment plan.

What is estimated chargeable income (ECI)?

Estimated chargeable income is your company’s own forecast of its taxable profit for the Year of Assessment, after tax-allowable expenses. IRAS uses it to raise an early Notice of Assessment, so tax is collected months before the full return arrives. You report only revenue and the ECI itself, rounded to the nearest dollar; IRAS works out the tax. The estimate should be realistic rather than perfect. Up-to-date management accounts, with non-deductible items such as fines, S-plated car costs and capital purchases added back, are a sensible starting point. A low number does not save tax; it just moves a larger bill later.

When is the ECI filing deadline?

The ECI filing deadline is three months after your financial year end, according to IRAS guidance on ECI filing. It follows your own year end, not the 30 November return date.

If you run several entities or recently changed your year end, our calendar of corporate tax submission deadlines maps every filing date by financial year end.

Do I qualify for the ECI waiver?

You qualify for the ECI waiver only when both conditions are true for that Year of Assessment: annual revenue is $5 million or below, and ECI is nil. Meet both and you simply do not file. As IRAS puts it in its corporate income tax obligations guide:

“There is no need to contact IRAS nor seek a confirmation that you need not file.” Inland Revenue Authority of Singapore (IRAS)

The edges catch people out. A company with revenue above $5 million must still complete its ECI filing even when the estimate is nil after a loss-making year. A company with $300,000 revenue and a small profit files too, because its ECI is not nil. The test resets every year.

By the numbers: IRAS assessed 291,192 companies in FY2024/25, yet only 114,709 of them were taxpaying, according to the IRAS Annual Report FY2024/25. With fewer than four in ten assessed companies paying tax, working out correctly whether the nil-ECI waiver applies is a real time saver for many SMEs.

How to file ECI on myTax Portal

Here is how to file ECI in three steps:

1. Set up Corppass access. Authorise the filer for Corporate Tax. A Preparer can draft the form, but only an Approver submits it. Using a tax agent? Authorise the agent instead.
2. Complete the form in myTax Portal. Confirm the financial year end (pre-filled from ACRA records), enter revenue and ECI, submit, and keep the acknowledgement number.
3. Arrange GIRO. Instalments only apply to companies paying by GIRO, so set it up before the Notice of Assessment arrives.

Why should I file ECI early?

Filing early buys time to pay. Companies on GIRO receive instalments based on when the ECI filing is made: 10 instalments if filed by the 26th of the first month after the financial year end, 8 if filed by the 26th of the second month, 6 if filed by the 26th of the third month, and none after that. IRAS describes these as interest-free monthly instalments. On an estimated tax bill of $12,000, that is the difference between ten payments of $1,200 and a single lump sum due within a month of the assessment.

What happens if I miss the ECI filing deadline or get it wrong?

Miss it and IRAS may estimate your income and issue its own assessment. That tax is still payable within one month, and IRAS reviews an objection only once your return is filed, so you may pay on a number you never chose. If your filed estimate proves wrong, amend the ECI or object to the assessment in myTax Portal, within two months of the Notice of Assessment. Our guide on what happens if you are late for corporate taxes covers the wider penalty picture, including late Form C-S returns.

How is ECI different from Form C-S?

ECI is an early estimate; Form C-S is the actual tax return. Every company files a return each year, but not every company files ECI.

A company that files nil ECI in March and then reports a healthy profit in November faces the full bill at once. For the eligibility rules behind the return itself, read our breakdown of Form C-S, Form C-S (Lite) and Form C.

Keep ECI and Form C-S on One Calendar

Treat ECI as the first half of the same job. Diarise your ECI filing deadline the day your year closes, recheck the waiver test, and file before the 26th of the first month for the full instalment plan. To hand over the whole cycle, our accounting and tax services include ECI filing within three months and Form C-S or Form C preparation, so your company tax filing Singapore obligations sit with one team from estimate to final assessment.

Frequently Asked Questions