Form C, C-S and C-S Lite filing — Timeline and processing benchmarks

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

Form C, C-S and C-S Lite filing is how Singapore companies declare their income to the Inland Revenue Authority of Singapore (IRAS) each Year of Assessment. Form C-S Lite is the simplest, for small companies with revenue up to S$200,000; Form C-S suits companies up to S$5 million; and Form C is the full return for everyone else.

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

Every company in Singapore must file an annual corporate income tax return declaring its chargeable income for the Year of Assessment (YA). IRAS offers three versions. Form C-S Lite is a streamlined return for the smallest companies; Form C-S is a simplified return; and Form C is the full return requiring financial statements and tax computations to be submitted.

The correct form depends on the company’s revenue and whether it meets the qualifying conditions, principally being incorporated in Singapore, deriving only income taxable at the prevailing 17% rate, and not claiming specified complex reliefs.

For related guidance, see Singapore Corporate Tax 2026: A Complete Guide to Rates, Exemptions and Filing.

Who files which form

Form C-S Lite is available to companies that qualify for Form C-S and have annual revenue of S$200,000 or below. Form C-S is available to companies with annual revenue of S$5 million or below that meet the qualifying conditions. Form C is required for all other companies, including those claiming carry-back of losses beyond the norm, group relief, or foreign tax credits requiring detailed disclosure.

Companies that do not qualify for the simplified forms must file Form C together with audited or unaudited financial statements and a tax computation.

Eligibility conditions for the simplified forms

To use Form C-S or C-S Lite, a company must be incorporated in Singapore, have annual revenue within the relevant cap, derive income taxable only at 17%, and not be claiming carry-back of current-year capital allowances or losses, group relief, investment allowance, foreign tax credit or tax deducted at source. Companies failing any condition file Form C.

The obligation to file rests on directors, and Section 62 of the Income Tax Act 1947 requires companies to furnish returns of income in the form and manner determined by the Comptroller.

See also our cross-site guide: EP and S Pass Salary Floors Rising in January 2027: Employer Audit and Renewal Planning Guide.

Form C, C-S and C-S Lite filing timeline and processing benchmarks

The filing deadline for corporate income tax returns is 30 November of each Year of Assessment, for the financial year ending in the preceding year. Filing is done electronically via the myTax Portal. Companies should first file their Estimated Chargeable Income within three months of financial-year end, then the full return by 30 November.

Assessment by IRAS follows filing; straightforward returns are processed and a Notice of Assessment issued in the following months, while returns selected for review take longer.

Fees, thresholds and numerical benchmarks

Key figures: Form C-S Lite revenue cap S$200,000; Form C-S revenue cap S$5,000,000; corporate tax rate 17%; e-filing deadline 30 November. There is no IRAS filing fee, but late filing can attract enforcement action, including summonses and composition amounts. Newly incorporated companies may benefit from start-up tax exemptions on their first chargeable income.

Common mistakes and gotchas

Frequent errors include filing Form C-S when a disqualifying claim (such as group relief) is present, missing the 30 November deadline, and inconsistent figures between the ECI and the final return. Companies also forget that the revenue caps refer to revenue (turnover), not profit, so a low-profit but high-turnover company may not qualify for the simplified forms.

Related guides and official resources

Further reading: Form C, C-S and C-S Lite filing — Costs and fees breakdown; Singapore Corporate Tax 2026: A Complete Guide to Rates, Exemptions and Filing; EP and S Pass Salary Floors Rising in January 2027: Employer Audit and Renewal Planning Guide.

Official sources: www.iras.gov.sg | www.asc.gov.sg | www.acra.gov.sg.

FAQs

What is the corporate tax filing deadline in Singapore?
Corporate income tax returns must be e-filed by 30 November of the Year of Assessment via the myTax Portal.

Who can use Form C-S Lite?
Companies that qualify for Form C-S and have annual revenue of S$200,000 or below.

What is the revenue cap for Form C-S?
Annual revenue of S$5 million or below, alongside the other qualifying conditions.

Do I still need to file ECI?
Yes. Most companies must file Estimated Chargeable Income within three months of financial-year end, separately from the annual return.

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.