Singapore corporate income tax compliance turns on four dates: the ECI three months after your financial year-end, the Notice of Assessment issued by IRAS, the tax payment within one month of that notice, and the annual Form C-S / C-S Lite / C due by 30 November.
ECI — within 3 months of financial year-end
The Estimated Chargeable Income (ECI) must be filed within three months after the end of the company's financial year. For example, if the FY ends on 31 December, the ECI deadline is 31 March of the following year.
Most companies are required to file an ECI unless they meet the IRAS administrative concession (annual revenue not more than SGD 5 million and ECI is nil for the YA).
Notice of Assessment — by 31 May
After filing the ECI, IRAS issues a Notice of Assessment (NOA) — typically by 31 May. The NOA sets out the tax payable based on the ECI filed.
Tax payment — within 1 month of the NOA
The company must pay the tax within one month from the date of the NOA, unless an instalment plan via GIRO is in place — in which case the tax is spread over up to 12 monthly instalments. Filing the ECI early generally entitles the company to a longer instalment period.
Form C-S / C-S Lite / C — by 30 November
The Corporate Income Tax Return — Form C-S, Form C-S Lite or Form C, depending on company size and complexity — must be filed by 30 November annually for the relevant Year of Assessment. After this filing, IRAS issues a final NOA which may be different from the earlier ECI-based assessment, and any balance is payable or refunded accordingly.
Singapore tax deadlines at a glance
| Item | Deadline | What happens |
|---|---|---|
| ECI filing | Within 3 months of FY-end | Company submits its Estimated Chargeable Income to IRAS. |
| Notice of Assessment (NOA) | By 31 May (typically) | IRAS issues the assessment based on the ECI filed. |
| Tax payment | Within 1 month from NOA date | Company pays the tax assessed (or via GIRO instalments). |
| Annual tax return | 30 November of the YA | Company files Form C-S, Form C-S Lite or Form C. |
A worked example
Suppose your company has a financial year ending 31 December 2024. The compliance calendar for the resulting Year of Assessment 2025 looks like this:
- By 31 March 2025 — file the ECI.
- By 31 May 2025 — expect the Notice of Assessment from IRAS.
- Within 1 month of the NOA date — pay the tax assessed (or set up GIRO).
- By 30 November 2025 — file Form C-S / C-S Lite / C for YA 2025.
If your financial year ends on a different date, simply shift the ECI deadline by the corresponding number of months — the rest of the framework still applies.
The bottom line
Singapore corporate tax compliance is built around four dates: ECI within three months of FY-end, NOA by 31 May, payment within one month, and the annual return by 30 November. Late filing or late payment can attract penalties and interest, so it pays to lock these dates into your finance calendar — or hand them to a tax advisor.
To learn more about how we support clients on tax matters, see our Corporate / Individual Tax services.