Form C, C-S and C-S Lite filing — Eligibility and requirements checklist

Form C, Form C-S and Form C-S (Lite) are the corporate income tax returns Singapore companies file with IRAS each year. The form a company uses depends on its revenue and complexity: C-S (Lite) for the smallest simple companies, C-S for small companies, and the full Form C for everyone else. The filing deadline is 30 November.

Raffles Corporate Services works with a panel of corporate and employment law firms; this article is general information, not legal advice.

What Form C, C-S and C-S (Lite) are

Every company carrying on business in Singapore must file an annual corporate income tax return declaring its chargeable income to the Inland Revenue Authority of Singapore. There are three variants of the return, and the correct one depends on the company’s size and the simplicity of its tax affairs. All three cover the same Year of Assessment and are filed electronically through myTax Portal.

Which form applies

Form C-S (Lite) is the simplest return, for small companies with annual revenue of S$200,000 or below that also meet the C-S qualifying conditions. Form C-S is for companies with annual revenue of S$5 million or below that meet the qualifying conditions. Form C is the full return for all other companies, and requires financial statements and tax computations to be submitted with it.

The qualifying conditions for C-S and C-S (Lite) are that the company is incorporated in Singapore, derives only income taxable at the prevailing 17% rate, and does not claim specified reliefs such as carry-back of capital allowances, group relief, investment allowance, foreign tax credit or the tax-exemption for foreign-sourced income. A company that claims those reliefs must file the full Form C. Our guide to carrying forward unutilised tax losses, Badges of Trade in Singapore (2026): Are Your Company’s Gains Ta, explains one of the reliefs that can push a company onto the full form.

Eligibility and requirements checklist

  • Confirm annual revenue to select the correct form: up to S$200,000 for C-S (Lite), up to S$5 million for C-S, above that for Form C.
  • Check that no disqualifying reliefs are claimed if using C-S or C-S (Lite).
  • Prepare the tax computation reconciling accounting profit to chargeable income.
  • For Form C, prepare financial statements and detailed tax computation for submission.
  • File through myTax Portal by 30 November of the Year of Assessment.

Cost, timeline and processing benchmarks

The dates and figures to plan around:

  • Filing deadline: 30 November each year for the relevant Year of Assessment.
  • Estimated Chargeable Income (ECI) is a separate, earlier filing due within three months of the financial year end.
  • Revenue thresholds: S$200,000 (C-S Lite) and S$5 million (C-S).
  • Professional fees for preparing a straightforward return commonly range from S$500 to S$2,500 depending on complexity.

Because the tax computation flows from the statutory accounts, the accounting framework you use matters; see our companion note that pairs with Singapore Corporate Tax 2026: Rates, Exemptions and Filing Guide. For the ECI step that precedes the return, read EntrePass 2026: A Founder’s Complete Walkthrough.

Common mistakes and gotchas

The most frequent errors are using C-S or C-S (Lite) while claiming a disqualifying relief, missing the 30 November deadline, and failing to reconcile the tax computation to the financial statements. Dormant companies still generally need to file unless they have been granted a waiver. Section 62 of the Income Tax Act 1947 requires companies to furnish a return of income, and the Comptroller may issue an estimated assessment where a return is late, so timely filing protects against an inflated assessment. Authoritative guidance is published by www.iras.gov.sg and accounting-standard context by www.acra.gov.sg.

FAQs

What is the difference between Form C, C-S and C-S (Lite)?
Form C-S (Lite) is for the smallest companies with revenue up to S$200,000; Form C-S is for companies with revenue up to S$5 million; Form C is the full return for all other companies.

When is the corporate tax return due?
The filing deadline is 30 November of the Year of Assessment; ECI is filed separately within three months of the financial year end.

Can I use Form C-S if I claim group relief?
No. Claiming reliefs such as group relief, carry-back, investment allowance or foreign tax credit disqualifies a company from C-S and C-S (Lite); it must file the full Form C.

Do dormant companies need to file?
Generally yes, unless IRAS has granted a waiver of the requirement to file for a dormant company.

Need help with this? Call, SMS or WhatsApp +65 8501 7133, or email [email protected]. Raffles Corporate Services works with a panel of corporate and employment law firms; this article is general information, not legal advice.