Every Singapore company files a corporate income tax return each year, and for most small companies that return is Form C-S. For Year of Assessment 2026, the deadline is 30 November 2026. It applies even if your company made a loss or had very little activity.
Form C-S is designed to be simple, and for many companies it takes less than an hour to complete once the figures are ready. The time goes into getting those figures ready. This guide walks you through which form to use, the key dates, what to prepare, each step on myTax Portal, and the mistakes we see most often.
Key Takeaways
IRAS offers three versions of the corporate income tax return:
Your company can file Form C-S if it meets all of these conditions:
Form C-S (Lite) has the same conditions, with revenue of S$200,000 or less. The details are set out on the IRAS overview of Form C-S, Form C-S (Lite) and Form C.
If any of the conditions above are not met, the company files Form C. Typical examples are companies with revenue above S$5 million, companies incorporated overseas with a Singapore branch, companies with income taxed at a concessionary rate, and companies claiming group relief or foreign tax credits.
Singapore taxes income on a preceding year basis. For YA2026, the basis period is the financial year that ended in 2025. If your company's year end is 31 December, you are reporting income for 1 January to 31 December 2025. If your year end is 30 June, you are reporting the year that ended on 30 June 2025. Our article on choosing a financial year end explains how this works if you are unsure.
All YA2026 corporate income tax returns are due by 30 November 2026, whichever form you use. IRAS publishes the year's filing guidance on its Corporate Income Tax Filing Season 2026 page.
Before Form C-S, many companies also need to file Estimated Chargeable Income (ECI) within three months of their financial year end. Companies with revenue of S$5 million or less and ECI of nil may not need to file it. Our guide to ECI filing covers this in detail.
If you miss the deadline, IRAS may:
An estimated assessment can only be revised by filing the actual return. It is far simpler to file on time.
A dormant company is still required to file unless IRAS has granted a waiver. If your company has stopped trading and has no income, you may apply for a waiver of the requirement to file. Until a waiver is granted, keep filing.
This is the part that takes the time. Have these ready before you log in.
You need your final accounts for the financial year, including the profit and loss statement and balance sheet. The revenue you declare on Form C-S should match the revenue in these accounts exactly. If you are still finalising your accounts, see our year-end checklist for what usually needs to be closed off.
The tax computation starts from your accounting profit and adjusts it to arrive at chargeable income. It adds back expenses that are not deductible, such as private expenses, depreciation, fines and certain donations, and deducts income that is not taxable or is taxed separately. Form C-S asks for figures that come straight from this computation.
You do not submit the tax computation with Form C-S. You must still prepare it and keep it, because IRAS can ask for it at any time.
If your company bought or sold equipment, computers, vehicles or other fixed assets, you will need a schedule showing capital allowances. Capital allowances replace accounting depreciation for tax purposes.
The person filing needs the right access. In Corppass, they should be assigned the "Corporate Tax (Filing and Applications)" e-Service, as either a preparer or an approver. A preparer can fill in the form, but only an approver can submit it. If your tax agent is filing, the company authorises them through Corppass as well. Sort this out early, because Corppass changes often stall in the final week.
IRAS updates the screens from time to time, so the labels you see may differ slightly. The flow below is what most small companies will go through.
Log in to myTax Portal with Singpass through Corppass. Go to Corporate Tax, then File Form C-S/ C-S (Lite)/ C. Select YA2026. The system will ask a few questions to confirm which form you are eligible for.
Check the company details shown, including the financial year end and principal activities. Answer the questions about the company's status, such as whether it is claiming any of the items that would make it ineligible for Form C-S. If any answer moves you out of Form C-S, the system will guide you to Form C instead.
This is the core of the form. You enter figures from your financial statements and tax computation, including revenue, adjusted profit or loss before other deductions, and items such as non-deductible expenses and non-taxable income. Take your time here and enter figures exactly as they appear in your workings.
Enter capital allowances for the year and any balances brought forward from earlier years. If the company has unutilised losses or capital allowances from previous years, these can generally be carried forward and set off against this year's income, subject to the shareholding test.
Review the summary page. Check the revenue figure, the chargeable income and the tax position against your tax computation. The approver then makes the declaration and submits the form.
After submission, you will see an acknowledgement page. Save or print it and keep it with the company's tax records. IRAS will issue the Notice of Assessment later, usually within a few months.
If your company's revenue is S$200,000 or less and it meets the other Form C-S conditions, you can file Form C-S (Lite). IRAS describes it as a simplified return with only six essential fields to complete. In practice, that means you type in a handful of key figures from your accounts and tax computation, starting with revenue, which is compulsory. Some items, such as unutilised capital allowances and losses brought forward from earlier years, are pre-filled by IRAS for you to check. It still relies on the same work behind it: your accounts and tax computation need to be prepared in the same way, even though fewer figures are entered on the form itself.
For many very small companies, such as consultancies, holding companies and early-stage startups, this makes filing noticeably quicker. If you are not sure whether you qualify, myTax Portal will check eligibility based on your answers at the start of the filing.
You do not need to calculate these yourself on Form C-S. IRAS applies them when it assesses your return. It still helps to understand them so you know what to expect. Our article on the YA2026 CIT rebate goes into more detail.
Budget 2026 announced a YA2026 corporate income tax rebate of 40%. On 7 April 2026, this was enhanced to 50% of tax payable, capped at S$40,000. Companies that employed at least one local employee in 2025 also receive a minimum benefit of S$2,000, paid as the CIT Rebate Cash Grant. The cash grant counts toward the overall S$40,000 cap, so the rebate given on assessment is reduced by any cash grant already paid.
Two exemption schemes reduce the chargeable income that is taxed:
A company can only use one of the two in any Year of Assessment. For a general overview of how these fit together, see our Singapore tax 2026 overview.
If you discover a mistake after submitting Form C-S, you can request a revision. If the Notice of Assessment has not been issued, you can usually make a revision through myTax Portal. If it has been issued, write to IRAS with the correct figures and an explanation, generally within four years from the end of the Year of Assessment. Making a voluntary correction promptly is treated more leniently than an error IRAS finds itself, under IRAS's voluntary disclosure programme.
No. With Form C-S and Form C-S (Lite), you do not submit financial statements or the tax computation. You must prepare them and keep them, and IRAS may ask for them later. With Form C, they are submitted together with the return.
Yes. Every company must file a return for YA2026 by 30 November 2026, whether it made a profit, a loss or had no income. Filing also records the loss so it can be carried forward to future years.
The form depends on the company's position for each Year of Assessment. If your company filed Form C last year but now meets all the Form C-S conditions, you can file Form C-S this year. The opposite also applies.
A person authorised in Corppass for the Corporate Tax (Filing and Applications) e-Service, either from the company itself or from an appointed tax agent. Only an approver can submit the return.
Form C-S is simple when the figures behind it are right. ATHR's tax and accounting team can:
With 30 November close, now is a good time to start. Talk to our tax team and we will help you file once, and file right.
This article is for general information only and reflects IRAS guidance available at the time of writing. It is not tax or professional advice. myTax Portal screens and requirements may change. Please refer to IRAS or speak to a qualified tax professional before filing.
The ATHR Content Team is a group of professional writers from Singapore and the Philippines, committed to delivering informative, practical, and engaging content for business owners across Southeast Asia.
