Every Singapore company must file a Corporate Income Tax Return with IRAS each year, but the form you use depends on your annual revenue. Filing the wrong form or missing the 30 November deadline can trigger penalties and estimated assessments.
The revenue thresholds that decide your form
IRAS offers three main filing options based on your company's annual revenue for the financial year being reported. Revenue means your main source of income and excludes separate sources such as interest or dividends.
| Form | Annual revenue threshold | Who it is for |
|---|---|---|
| Form C-S (Lite) | $200,000 or below | Smallest companies with straightforward tax affairs |
| Form C-S | $5 million or below | Small and medium companies that meet qualifying conditions |
| Form C | Above $5 million, or does not qualify for Form C-S | Larger companies or those with complex tax matters |
If your company qualifies for Form C-S (Lite), you may still choose to file Form C-S or Form C instead. The choice is yours, but you cannot move in the opposite direction—a company with revenue above $5 million must file Form C.
Other qualifying conditions for Form C-S and Form C-S (Lite)
Meeting the revenue threshold is not enough. Your company must also be incorporated in Singapore and must not derive income that is tax-exempt or taxed at concessionary rates (such as where tax incentives are granted), with limited exceptions. Companies with related-party transactions exceeding $15 million in value or that hold investment properties must also file Form C.
What each form requires you to submit
Form C-S (Lite): six essential fields
Form C-S (Lite) is the simplest option. It requires only six essential fields to be completed, covering basic information such as your adjusted profit or loss before capital allowances, rental income and donations. The entire form takes around ten minutes to complete online at mytax.iras.gov.sg.
Form C-S: 18 fields with more detail
Form C-S requires 18 fields, including tax adjustments and information drawn from your financial statements. It takes about ten to fifteen minutes to complete. Both Form C-S and Form C-S (Lite) filers do not need to submit financial statements, tax computation or supporting schedules at the time of filing. However, you must prepare these documents and be ready to submit them if IRAS requests them during a review.
Form C: full submission required
If you file Form C, you must submit your audited or unaudited financial statements, a detailed tax computation and all supporting schedules together with the form. IRAS estimates this takes around 30 minutes to complete. Form C is mandatory for companies that do not meet the Form C-S thresholds or qualifying conditions.
The 30 November deadline applies to all three forms
All companies must file their Corporate Income Tax Return by 30 November each year, regardless of which form they use. For example, a company with a 31 December 2025 financial year-end must file its Year of Assessment 2026 return by 30 November 2026. The basis period—the twelve-month financial year preceding the Year of Assessment—determines which year's income you report.
Late or non-filing is an offence. IRAS may issue an estimated Notice of Assessment, charge composition amounts of up to $5,000 per offence, or prosecute directors. If convicted in court, your company may face fines of up to $5,000, and directors can face fines of up to $10,000 or imprisonment of up to twelve months, or both.
Companies that adopt seamless filing from accounting software and file Form C-S through that route automatically receive a fifteen-day extension (to 15 December) for Years of Assessment 2023 to 2027, without needing to apply separately.
Why a simpler form does not mean a looser computation
Filing Form C-S (Lite) or Form C-S does not reduce your obligation to prepare proper financial statements and a complete tax computation. IRAS profiles companies based on complexity and risk, and conducts reviews on a percentage of companies with straightforward affairs each year. Companies with simple tax matters generally see their declarations accepted upfront, but IRAS may request full documentation at any time.
When you file Form C-S or Form C-S (Lite), you are declaring that your tax computation is correct. Common mistakes—such as claiming non-deductible expenses, understating income, or completing the adjusted profit or loss field incorrectly—can trigger audits or penalties. The computation behind a six-field Form C-S (Lite) must be just as accurate as the computation behind a full Form C.
If you are uncertain about which expenses are deductible or how to compute capital allowances, our guide to IRAS tax audits and what triggers them explains the areas IRAS focuses on during reviews.
What business owners should do
- Check your company's annual revenue for the financial year and confirm which form you qualify to file.
- Prepare complete financial statements and a tax computation every year, even if you file Form C-S (Lite) and do not submit them upfront.
- File by 30 November to avoid penalties, estimated assessments and potential prosecution.
- Keep all supporting records—receipts, invoices, bank statements—for at least five years in case IRAS requests them.
- If your revenue exceeds $5 million for the first time, be ready to file Form C the following year and submit full documentation with the return.
Steadbook prepares accurate tax computations, files corporate tax returns and keeps your company compliant with IRAS requirements year-round. Whether you qualify for Form C-S (Lite) or must file Form C, we ensure your figures are correct and your deadlines are met. Learn more about our accounting and tax services or contact us to discuss your company's tax filing.
Your annual revenue determines whether you file Form C-S, Form C-S (Lite) or Form C, but all three require accurate tax computations and timely filing by 30 November. Prepare full documentation every year, even if you qualify for the simplest form, because IRAS may request it during a review.