The practical bottom line: most Singapore companies must file their Estimated Chargeable Income (ECI) within three months of their financial year-end. You are only excused if your annual revenue is S$5 million or below and your ECI is nil — both conditions, not just one. Miss the deadline and IRAS can issue its own estimated tax bill, which you have to pay even while you argue about it. Filing early is not just tidy — it can also unlock up to ten interest-free GIRO instalments.

Here is what that means for your business, in plain terms.

What ECI is (and how it differs from Form C-S/C)

ECI is your company’s early estimate of its taxable income for a financial year. You file it before your full accounts are finalised, using your management figures. It is separate from your annual Corporate Income Tax Return (Form C-S, Form C-S (Lite) or Form C), which is due by 30 November. Think of ECI as the early heads-up and the Form C-S/C as the final word.

When is ECI due?

Generally, within three months from the end of your financial year — and the clock runs off your financial year-end, not the calendar year. So:

  • Financial year-end 31 December → ECI due 31 March
  • Financial year-end 31 March → ECI due 30 June
  • Financial year-end 30 June → ECI due 30 September

IRAS usually sends a filing notification in the last month of your financial year. Important: if the reminder does not arrive and you do not qualify for the waiver, you must still file on time.

Who is exempt — the ECI filing waiver

You do not need to file ECI for a Year of Assessment when both of these are true:

  1. Your annual revenue is S$5 million or below for the financial year; and
  2. Your ECI is nil for the Year of Assessment (measured before deducting the start-up or partial tax exemption).

Meet only one and you still have to file. A common trap: a company with revenue above S$5 million but nil estimated income still has to file — you simply enter the ECI as zero. The reassuring part is that when you do qualify for the waiver, there is no need to seek confirmation from, or inform, IRAS. Whether or not the waiver applies, you must still file your Form C-S/C by 30 November.

What happens if you file late

If your company is required to file ECI but does not do so within the three-month window, IRAS may issue a Notice of Assessment (NOA) based on its own estimate of your income. That estimate can be higher than your actual position. You can object — generally within two months of the NOA date — but the tax demanded must usually be paid first while the objection is reviewed. In short: a late or missed ECI often means paying more, sooner, and clawing it back later.

Filing early can smooth your cash flow

Here is the upside most SMEs overlook. If your company is Singapore-registered and on GIRO, the number of interest-free instalments you get depends on how early you file:

  • File by the 26th of the 1st month from your financial year-end → up to 10 instalments
  • File by the 26th of the 2nd month → up to 8 instalments
  • File by the 26th of the 3rd month → up to 6 instalments
  • File after the 3rd month → no instalments (pay in full)

If you do not already have a GIRO arrangement for Corporate Tax, apply early — GIRO must be approved before the payment due date for you to enjoy instalments.

A simple checklist for your ECI

  1. Confirm your exact financial year-end and count three months forward.
  2. Close enough of your accounts to estimate taxable profit for the year.
  3. Test the two waiver conditions separately — revenue and nil ECI.
  4. If filing, aim for the 26th of month one, two or three to keep more instalments.
  5. e-File via myTax Portal (mytax.iras.gov.sg) using Corppass, and save the acknowledgement.

Subject to your company’s facts, getting ECI right is usually straightforward once your bookkeeping is current — which is exactly why a clean, up-to-date set of books pays off at year-end.

Speak with BTA

Not sure whether the waiver applies to you, or want your ECI and instalment timing handled properly? Speak with BTA to review your position — we help Singapore SMEs keep their corporate tax compliance accurate and on time, and keep your accounts and bookkeeping ready for filing.

Call +65 6250 4321 · businesstaxaccountancy.com.sg

General information for Singapore businesses, current as at August 2026 and subject to your company’s facts and prevailing IRAS rules — not tax advice.