Form C, C-S and C-S Lite filing — Complete 2026 guide

Form C, C-S and C-S Lite filing is how a Singapore company reports its chargeable income to the Inland Revenue Authority of Singapore (IRAS) each Year of Assessment. This 2026 guide explains which form your company uses, the qualifying conditions, the deadlines, and the documents you must keep, so Form C, C-S and C-S Lite filing is handled correctly.

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 a trade or business in Singapore must file an annual Corporate Income Tax Return with IRAS. There are three variants. Form C-S Lite is the simplest, for small companies with straightforward affairs. Form C-S is the simplified return for qualifying companies. Form C is the full return for companies that do not qualify for the simplified forms, including those claiming certain reliefs or with foreign income complexities.

The return reports the company’s chargeable income after tax adjustments. It is filed together with the tax computation and, where required, the financial statements and supporting schedules.

Who qualifies for each form

The three-tier system is built around size and simplicity:

  • Form C-S Lite: annual revenue of S$200,000 or below, and the company meets the Form C-S qualifying conditions.
  • Form C-S: incorporated in Singapore, annual revenue of S$5,000,000 or below, deriving only income taxable at the prevailing 17% rate, and not claiming specified reliefs such as carry-back of losses beyond the current year, group relief, investment allowance or foreign tax credit.
  • Form C: any company that does not qualify for C-S or C-S Lite, including those claiming group relief. See our companion guide to group relief and loss transfer under section 37B for how those claims affect your filing.

Eligibility conditions in detail

The qualifying conditions exist to streamline filing for ordinary trading companies. A company claiming reliefs that require detailed schedules, or one with income taxed at concessionary rates, must use Form C so that IRAS receives the full computation. Investment holding companies and service companies have specific treatment; their revenue and income profile determines the correct form.

Cost, timeline and the filing calendar

Corporate tax filing follows a fixed annual rhythm:

  • e-Filing deadline: 30 November of the Year of Assessment for all three forms.
  • Estimated Chargeable Income: due within 3 months of the financial year-end unless the company is exempt from filing ECI.
  • Headline tax rate: 17% on chargeable income.
  • Record retention: business records must be kept for at least 5 years.
  • Filing fee: there is no IRAS charge to e-file; cost arises from preparation and accounting work.

Sound bookkeeping is the foundation of an accurate return; see our guide to bookkeeping for Singapore SMEs for the records you need to maintain through the year.

Step-by-step: filing your Corporate Income Tax Return

  1. Finalise the financial statements for the financial year.
  2. Prepare the tax computation, adjusting accounting profit for non-deductible expenses, capital allowances and exempt income.
  3. Determine which form the company qualifies to file.
  4. Authorise the filing person or tax agent in Corppass.
  5. e-File the return through the IRAS myTax Portal by 30 November.
  6. Retain the computation, financial statements and supporting documents for at least 5 years.

Statutory basis

The obligation to file rests on the Income Tax Act 1947. Section 62 of the Income Tax Act 1947 addresses the Comptroller’s power to require returns, and section 71 of the Income Tax Act 1947 deals with the consequences of failing to furnish a return, including estimated assessments. Filing the correct form with an accurate computation is therefore a statutory duty, not a discretionary administrative step.

Common mistakes and gotchas

Typical errors include filing Form C-S while claiming a relief that disqualifies the company from the simplified form, missing the 30 November deadline, omitting capital allowance schedules, and failing to reconcile the tax computation to the financial statements. Where a company files the wrong form, IRAS may require resubmission, delaying the assessment.

Authoritative sources

Refer to IRAS guidance on corporate income tax filing at iras.gov.sg, accounting standards set by the Accounting Standards Committee, and statutory filing requirements administered by ACRA.

Frequently asked questions

What is the deadline for Form C, C-S and C-S Lite?
All three are e-Filed by 30 November of the Year of Assessment. There is no paper filing option.

Can a dormant company file a simpler return?
A dormant company may be required to file a return unless IRAS has granted a waiver. Where it must file, it submits the return appropriate to its circumstances.

Do I need to submit financial statements with the form?
Form C requires financial statements and the tax computation. Form C-S and C-S Lite do not require the documents to be submitted, but they must be prepared and retained for IRAS on request.

What if I file the wrong form?
IRAS may ask the company to resubmit using the correct form, which can delay the notice of assessment. Confirming eligibility before filing avoids the issue.

Related guides

For wider context, see our group relief and loss transfer under section 37B, our Employment Pass and S Pass salary thresholds, and bookkeeping for Singapore SMEs.

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.