Form C, C-S and C-S Lite filing — Step-by-step walkthrough

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

Understanding form c, c-s and c-s lite filing is essential for 2026. Form C, Form C-S and Form C-S (Lite) are the three corporate income tax returns a Singapore company may file with IRAS, and choosing the right one depends on the company's revenue and circumstances. This walkthrough explains the eligibility for each, what each return requires, and the filing timeline for the 2026 cycle.

What Form C, C-S and C-S (Lite) are – form c, c-s and c-s lite filing

Every Singapore company must file an annual corporate income tax return reporting its income for the relevant Year of Assessment. IRAS provides three forms: Form C-S (Lite) for the smallest companies, Form C-S for small companies meeting the simplified conditions, and Form C for everyone else, including companies that must submit full supporting documentation.

The corporate tax return obligation flows from the Income Tax Act 1947, which requires companies to furnish a return of income in the form and manner determined by the Comptroller of Income Tax.

For corporate-secretarial and related context, see Complete Guide to Setting Up a Family Office in Singapore (2026). Our companion article Form C, C-S and C-S Lite filing — Complete 2026 guide covers a related angle.

Who is eligible for each form

Form C-S is available to a company that is incorporated in Singapore, has annual revenue of S$5 million or below, derives only income taxable at the prevailing corporate rate, and is not claiming specified complex reliefs such as carry-back of capital allowances or foreign tax credit. Form C-S (Lite) is a further-simplified version for companies with annual revenue of S$200,000 or below that meet the same qualifying conditions.

A company that does not meet the Form C-S conditions – for example, one claiming group relief or foreign tax credits – files Form C and submits its financial statements and tax computation.

On the immigration and employment side, see EP vs S Pass vs EntrePass: The Complete Singapore 2026 Comparison Guide.

What each return requires

Form C-S (Lite) asks for a minimal set of fields, principally revenue, adjusted profit and a handful of declarations. Form C-S requires the same core figures with additional information but still does not require financial statements and tax computation to be filed with the return, although these must be prepared and kept. Form C requires financial statements, the tax computation and supporting schedules to be filed.

In all cases the company must prepare a proper tax computation reconciling accounting profit to chargeable income, even where it is not filed, because IRAS can request it.

The filing timeline and e-Filing

Corporate income tax returns are filed electronically through the IRAS myTax Portal, and the filing deadline is 30 November of the Year of Assessment. The Year of Assessment is the year following the company's financial year end, so a company with a 31 December 2025 financial year end files for YA 2026 by 30 November 2026.

This sits separately from the Estimated Chargeable Income filing, which is generally due within three months of the financial year end and represents an earlier estimate of the same income.

Cost, timeline and getting it right

Professional preparation of a corporate tax computation and return for a Singapore SME commonly ranges from S$600 to S$2,000 depending on complexity. A straightforward Form C-S can be completed within a week of finalised accounts; Form C with full schedules takes longer.

File early. Leaving the 30 November deadline to the last week risks portal congestion and leaves no margin to resolve queries on reliefs or capital allowances.

Common mistakes and gotchas

Companies frequently file the wrong form after crossing the revenue threshold, forget that Form C-S still requires a tax computation to be kept, and overlook the separate ECI obligation. Each is avoidable with a simple eligibility check before filing.

Step-by-step: choosing and filing the right form

First, check eligibility against the current Year of Assessment. Confirm the company is Singapore-incorporated, calculate annual revenue, and confirm it derives only income taxable at the prevailing rate and claims none of the excluded reliefs. Revenue of S$200,000 or below points to Form C-S (Lite); up to S$5 million points to Form C-S; anything else, or any excluded relief, means Form C.

Second, prepare the tax computation regardless of the form. Even where financial statements and the computation are not filed with Form C-S or C-S (Lite), they must be prepared and retained, because IRAS can request them and a missing computation is a compliance gap.

Third, e-file through myTax Portal before 30 November of the Year of Assessment, retaining the acknowledgement. File early enough to resolve any portal authorisation issues, which are a common last-minute obstacle for companies whose CorpPass roles are not set up.

Numbers that matter: thresholds, fees and deadlines

The thresholds to remember are S$200,000 (Form C-S Lite ceiling) and S$5 million (Form C-S ceiling), and the hard deadline of 30 November of the Year of Assessment. Professional preparation for an SME commonly costs S$600 to S$2,000 depending on complexity. The Year of Assessment is the year after the financial year end, so a 31 December 2025 year end is assessed in YA 2026.

These dates dovetail with the Estimated Chargeable Income deadline three months after year end, so the two filings should be planned together rather than treated as separate events.

Related guides and where to go next

The corporate tax return draws directly on the SFRS financial statements and on the earlier ECI estimate, so reading the three together gives a coherent compliance calendar. The cross-references here point to the related accounting and family-office resources across the group.

Where a company claims group relief, foreign tax credits or carry-back of losses, the move to Form C and full schedules warrants professional support, and Raffles Corporate Services can assist.

Official sources and further reading

Always verify the current position against the primary sources: www.iras.gov.sg, www.asc.gov.sg, www.acra.gov.sg.

FAQs

Can I switch between forms year to year?
Yes. Eligibility is assessed each Year of Assessment, so a growing company may move from C-S (Lite) to C-S to Form C as revenue and complexity increase.

Is the filing deadline really 30 November?
Yes, corporate income tax returns are due by 30 November of the Year of Assessment, e-filed through myTax Portal.

Do I still need financial statements for Form C-S?
They are not filed with the return, but they and the tax computation must be prepared and retained for IRAS on request.

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.