Singapore Corporate Tax Filing: Form C-S, C-S (Lite) and C (2026)

Form C-S, Form C-S (Lite), and Form C are all the same thing at heart: a Corporate Income Tax Return in which your company declares its actual income for a Year of Assessment. The difference is how much detail each one asks for. The full overview is on the IRAS Form C-S overview page, and the current cycle is set out on the IRAS Corporate Income Tax Filing Season 2026 page.

One point catches founders out every year: you must file even if your company received no income or made a loss. A nil return is still a return. The only companies that skip filing are those IRAS has granted a waiver, and dormant companies, which can file the simpler Form for Dormant Company instead.

Form C-S

Form C-S is a simplified return for qualifying smaller companies, with fewer fields than Form C. It comprises a declaration of eligibility, information on tax adjustments, and information from the financial statements. You do not attach financial statements or a tax computation, but you must prepare them and be ready to submit on request.

Form C-S (Lite)

Form C-S (Lite) is a further simplified version of Form C-S, requiring only 6 essential fields, for companies with straightforward tax matters and the lowest revenue band. Like Form C-S, it needs no attachments, only readiness to produce them on request.

Form C

Form C is the full return for any company that does not qualify for the simpler forms. With Form C, you must attach your financial statements, tax computation, and supporting documents.

Most guides reduce Form C-S eligibility to one line about revenue. There are actually four conditions, and the last one is where companies trip up.

The four conditions

Your company qualifies to file Form C-S if it is incorporated in Singapore, has annual revenue of S$5 million or below, derives only income taxable at the prevailing corporate tax rate of 17%, and is not claiming any of four specific items in the Year of Assessment: carry-back of current year capital allowances or losses, group relief, investment allowance, or foreign tax credit and tax deducted at source. If you claim any of those four, you file Form C, regardless of your revenue.

Form C-S (Lite) adds one condition

Form C-S (Lite) has exactly the same conditions as Form C-S, with one addition: annual revenue of S$200,000 or below. The only difference between the two forms is that revenue threshold. A company that qualifies for Form C-S (Lite) can still choose to file Form C-S or Form C if it prefers.

The concessionary-income exception

Form C-S should not be filed if your company derives income that is tax exempt or taxed at concessionary rates, for example where a tax incentive applies. There are two carve-outs: one-tier tax-exempt Singapore dividends, and specified foreign-sourced income exempted under Section 13(8) of the Income Tax Act 1947. Outside those, concessionary or exempt income pushes you to Form C.

The File Form C-S and Form C-S (Lite) digital service for YA 2026 is available on myTax Portal. The steps below follow the IRAS Form C filing guidance.

Step 1, Confirm your form

Confirm that your company meets the Form C-S conditions. If your revenue is S$200,000 or below, you can choose Form C-S (Lite).

Step 2, Sort out Corppass and Singpass

Make sure you are authorised as an Approver for Corporate Tax (Filing and Applications) in Corppass, and have your Singpass and your company's UEN ready. Corppass authorisation can take time if it is not already set up, so do not leave it to filing day.

Step 3, Have your figures ready

Even though you do not attach them, you need your financial statements and tax computation to complete the fields accurately. Prepare them first.

Step 4, File on myTax Portal

File via myTax Portal. At the Form Type Selection step, choose Form C-S, or Form C-S (Lite) if it is offered. IRAS suggests setting aside at least 10 minutes to complete either form.

Step 5, Submit and keep records ready

Submit the return and keep your financial statements and tax computation on hand, since IRAS can request them later. If you would rather have a professional handle this, you can compare Singapore accounting providers that handle Form C filing.

Form C is more involved because you attach your supporting documents. The IRAS Form C filing guidance covers it in full.

Step 1, Confirm you must file Form C

You file Form C if you do not qualify for Form C-S or Form C-S (Lite), for example because you claim group relief or have concessionary income.

Step 2, Sort out Corppass and Singpass

As with Form C-S, be authorised as an Approver for Corporate Tax in Corppass, and have your Singpass and UEN ready.

Step 3, Prepare your documents as PDFs

Have your financial statements, detailed profit and loss statement, tax computation, and other supporting documents ready in softcopy. IRAS requires PDF format. A practical note from IRAS: use a font size of at least 11, and if you need to reduce file size, scan at 100dpi black and white. Companies that are small enough for audit exemption attach unaudited financial statements here; our Singapore small company audit exemption guide explains who qualifies.

Step 4, File and attach on myTax Portal

File Form C via myTax Portal and attach the financial statements, detailed profit and loss statement, tax computation, and supporting documents. IRAS suggests setting aside at least 30 minutes to complete Form C.

Step 5, Submit

Submit the return with everything attached. If preparing a full Form C with a tax computation is more than you want to take on in-house, see our Singapore accounting and bookkeeping comparison for providers that do it end to end.

The corporate tax return is the end of a sequence, not the start. Understanding what comes before it prevents double counting and surprises.

ECI comes first

Your company files its Estimated Chargeable Income within 3 months of its financial year end, as an early estimate. The Form C-S, Form C-S (Lite), or Form C is the final return, due by 30 November. One detail to get right across both: the chargeable income you declare in the ECI and in the Corporate Income Tax Return should not include the CIT Rebate. Our Singapore ECI filing guide covers the upstream step, and the IRAS ECI filing page is the source.

The CIT Rebate is computed automatically

For YA 2026, the CIT Rebate is 50% of corporate tax payable, capped at S$40,000, computed automatically from the ECI or Form C you file, so there is no separate claim. The parameters are on the IRAS Corporate Income Tax Rebates page.

A first set of accounts longer than 12 months

If your company's first set of financial statements covers more than 12 months from incorporation, you split the result across two Years of Assessment, because the basis period for each YA cannot exceed 12 months. You attribute the adjusted profit or loss before other deductions to the two YAs and complete the line items for both, using a time apportionment basis if you cannot attribute directly. The mechanics are in the IRAS Form C filing guidance.

1. Assuming a dormant or loss-making company does not file. It does, by 30 November, unless granted a waiver. A dormant company can use the simpler Form for Dormant Company.
2. Filing Form C-S while claiming a disqualifying item. Group relief, carry-back of current year capital allowances or losses, investment allowance, or foreign tax credit each forces you to Form C, whatever your revenue.
3. Filing Form C-S on concessionary or exempt income. That is not allowed, except for one-tier exempt Singapore dividends and Section 13(8) foreign-sourced income.
4. Leaving Corppass to the last minute. You must be an authorised Approver for Corporate Tax before you can file, and setting that up takes time.
5. Splitting a long first period wrongly. If your first accounts run more than 12 months, the result is attributed across two Years of Assessment, not declared in one.
6. Including the CIT Rebate in your declared income. The rebate is computed automatically; do not net it into the chargeable income you report.
7. Treating Form C-S (Lite) as a different obligation. It is the same return as Form C-S with fewer fields; if your revenue rises above S$200,000, you simply file Form C-S instead for that year.