Quick answer: Every Singapore company files one corporate income tax return with IRAS each year, by 30 November. The form depends mainly on revenue:
- Form C-S (Lite): revenue of S$200,000 or below
- Form C-S: revenue of S$5 million or below
- Form C: everyone else, or any company that fails the Form C-S conditions
Most newly incorporated companies qualify for Form C-S (Lite).
Form C-S vs Form C-S (Lite) vs Form C at a glance
| Form C-S (Lite) | Form C-S | Form C | |
|---|---|---|---|
| Annual revenue | S$200,000 or below | S$5 million or below | No limit |
| Who can file | Singapore-incorporated companies meeting all Form C-S conditions | Singapore-incorporated companies meeting all conditions below | All companies |
| Fields to complete | 6 | 18 | Full return |
| Submit financial statements? | No (keep ready for IRAS) | No (keep ready for IRAS) | Yes |
| Submit tax computation? | No (keep ready for IRAS) | No (keep ready for IRAS) | Yes |
| Deadline | 30 November | 30 November | 30 November |
| Best for | New and micro companies | Small companies with simple tax affairs | Larger companies, incentive holders, groups |
Who can file Form C-S?
Revenue is only one of four conditions. A firm can file Form C-S only if it meets all of them:
1. It is incorporated in Singapore.
2. Its annual revenue is S$5 million or below.
3. All its income is taxed at the standard 17% corporate tax rate.
4. It is not claiming any of these in the Year of Assessment:
- Carry-back of current-year capital allowances or losses
- Group relief
- Investment allowance
- Foreign tax credit or tax deducted at source
What trips companies up: condition 3 and the foreign tax credit exclusion. Suppose your company has a tax incentive, concessionary-rate income, or wants to claim credit for foreign withholding tax. Then it must file Form C, even with revenue far below S$5 million. One-tier Singapore dividends and specified exempt foreign income don’t disqualify you.
Who can file Form C-S (Lite)?
Form C-S (Lite) has the same conditions as Form C-S, with one difference: revenue must be S$200,000 or below.
- Revenue, cost of sales, gross profit, total costs, net profit or loss, and tax adjustments are the only six essential numbers that are requested.
- myTax Portal offers the Lite option automatically when you enter revenue of S$200,000 or below.
- A company that qualifies for Lite can still choose Form C-S or Form C.
When do you need Form C?
File Form C if your company:
- Has revenue above S$5 million
- Has income that is tax-exempt or taxed at a concessionary rate under an incentive
- Claims group relief, loss carry-back, investment allowance or foreign tax credits
- Is incorporated outside Singapore (for example, a Singapore branch of a foreign firm)
Form C requires the financial statements, tax computation and supporting documents to be submitted with the return.
Key filing rules for every company
- One deadline for all forms: 30 November each year, filed electronically on myTax Portal.
- How the Year of Assessment (YA) works: the YA is the year after your financial year. A company with a 31 December 2025 year-end files its YA 2026 return by 30 November 2026.
- Losses and zero income still need a return: a company must file even if it earned no income or made a loss.
- ECI comes first: Estimated Chargeable Income is due within 3 months of your financial year-end. It’s waived only if revenue is S$5 million or below and ECI is nil.
- Payment: Tax assessed on the Notice of Assessment is payable within one month.
- Dormant companies can file Form C-S or IRAS’s Form for Dormant Company instead.
Ongoing compliance obligations beyond the tax return
Filing the right form is one part of the picture. Every Singapore company also has these year-round duties:
1. Keep proper records for at least 5 years
Keep invoices, receipts, bank statements, contracts and ledgers that support your financial statements and tax computation. Form C-S filers don’t submit these, but IRAS can ask for them at any time.
2. Maintain statutory registers
Registers of members, directors, secretaries, and auditors must be maintained by your organisation.
Additionally, it must maintain a register of registrable controllers—those who ultimately own or control it—and provide that data to ACRA. Nominee directors and shareholders must also be declared to ACRA since the 2025 revisions.
3. Appoint an auditor, unless you qualify as a small company
A private company is exempt from audit if it meets at least 2 of these 3 criteria:
| Criterion | Threshold |
|---|---|
| Total annual revenue | S$10 million or less |
| Total assets | S$10 million or less |
| Employees | 50 or fewer |
Timing: the test applies to the two immediately preceding financial years. A newly incorporated company only needs to meet it in its current year.
Foreign-owned subsidiaries, take note: if your Singaporean business is part of a group, the group as a whole must also pass the test. An audit may nevertheless be necessary for a tiny Singaporean subsidiary of a major international parent.
Financial statements must still be prepared and submitted with the yearly return by audit-exempt businesses.
4. Keep ACRA updated
Notify ACRA when you change directors, company secretary, shareholders, registered office address or business activity. Late updates can lead to penalties and leave your public company profile out of date.
Common mistakes to avoid
- Filing Form C-S while holding a tax incentive or claiming a foreign tax credit
- Assuming no revenue means no filing
- Missing the ECI deadline because the company is new
- Assuming a subsidiary is audit-exempt without running the group test
- Letting the register of registrable controllers fall out of date after a share transfer
How OnDemand International helps?
OnDemand International handles your company’s full annual compliance cycle:
- Choosing the correct tax form
- Preparing financial statements and tax computations
- Filing ECI and your corporate tax return
- Running the audit-exemption test
- Keeping your ACRA registers current
Explore our corporate compliance services. If you’re still setting up, start with our guide to Singapore company registration.
Conclusion
Choosing the right tax form is essential for Singapore corporate tax compliance. Form C-S (Lite) suits eligible micro businesses, Form C-S is designed for qualifying small companies, and Form C applies to larger businesses or those with complex tax requirements.
Need help with Singapore corporate tax filing? OnDemand International offers expert assistance with tax returns, financial reporting, and regulatory compliance.
Contact OnDemand International today for a consultation and ensure your Singapore business stays compliant!