Every incorporated company in Singapore is required to file a corporate income tax return with the Inland Revenue Authority of Singapore (IRAS) each year. But there are two forms — Form C and Form C-S — and filing the wrong one (or missing the deadline) can result in penalties.
Who Needs to File?
All companies incorporated in Singapore — including dormant companies and companies with no income — must file a corporate income tax return (Form C or Form C-S) with IRAS every year. Filing is mandatory regardless of whether your company made a profit.
💡 Even if your company made a loss or had zero revenue, you are still required to file. Non-filing attracts penalties and IRAS may issue estimated assessments.
What is Form C-S?
Form C-S is a simplified version of the corporate tax return, designed for small companies. It is a 3-page document that contains fewer fields and no requirement to attach financial statements or tax computation to IRAS — though you must still prepare and retain these records.
Your company qualifies for Form C-S if it meets all three criteria:
- Annual revenue of S$5 million or less
- Only derives income taxable at the prevailing corporate tax rate (currently 17%)
- Does not claim any of the following: capital allowances carry-back, group relief, investment allowance, foreign tax credit, or tax deducted at source
What is Form C?
Form C is the full corporate income tax return. It is more comprehensive and requires companies to submit the return together with financial statements, tax computation, and supporting schedules.
Your company must file Form C if it does not qualify for Form C-S — for example if your revenue exceeds S$5 million, if you have tax adjustments to declare, or if you are claiming specific reliefs not available under Form C-S.
Key Differences at a Glance
| Criteria | Form C-S | Form C |
|---|---|---|
| Revenue threshold | ≤ S$5 million | Any revenue |
| Attachments required | None (retain records only) | Financial statements + tax computation |
| Length | 3 pages | Comprehensive |
| Tax rate claimed | 17% flat only | All rates and reliefs |
| Who uses it | Small companies | Larger or complex companies |
Common Mistakes to Avoid
- Filing Form C-S when your revenue actually exceeds S$5 million
- Missing the 30 November deadline (IRAS imposes late filing penalties)
- Failing to retain underlying financial statements even when using Form C-S
- Omitting capital allowances or loss carry-forward claims incorrectly
Deadlines You Must Know
The deadline for both Form C and Form C-S is 30 November each year (for the Year of Assessment). IRAS also requires companies to submit their Estimated Chargeable Income (ECI) within 3 months of the financial year-end — unless exempt.