Filing corporate tax in Singapore means making two separate submissions to the Inland Revenue Authority of Singapore (IRAS) each year — the Estimated Chargeable Income (ECI) within three months of your financial year end, and the Corporate Income Tax Return (Form C-S, Form C-S (Lite) or Form C) by 30 November.
Treating these as one filing is the most common and most expensive misunderstanding among first-time directors. Missing the Form C-S deadline can result in an estimated Notice of Assessment issued on IRAS’s own projection of your income, a late filing penalty, and in unresolved cases a summons to the company’s directors.
This guide walks through the full submission path in order: working out your basis period, filing ECI, choosing the right form, preparing the tax computation, and submitting through myTax Portal.
Step 1: Identify Your Basis Period and Year of Assessment
Singapore taxes companies on a preceding year basis. Income earned in the financial year ending in 2025 is assessed in Year of Assessment (YA) 2026.
Your basis period is simply your financial year. A company with a 31 December 2025 financial year end has a basis period of 1 January to 31 December 2025, assessed in YA 2026. A company with a 30 June 2025 financial year end has a basis period of 1 July 2024 to 30 June 2025, also assessed in YA 2026.
Get this right before anything else. Every deadline that follows is measured from your financial year end, not from the calendar year.
Step 2: File Your ECI Within Three Months of Financial Year End
ECI is your estimate of taxable income for the financial year, and it is generally due within three months from the end of that year [1].
Two points that save unnecessary work:
- The ECI figure excludes the exemptions. You declare chargeable income before applying the tax exemption scheme for new start-up companies or the partial tax exemption. IRAS computes and allows those automatically [1].
- A waiver may apply. A company may be waived from filing ECI where annual revenue for the financial year does not exceed S$5 million and the ECI is nil. If you are unsure whether you meet both conditions, file rather than assume.
An ECI that turns out to be materially different from your eventual Form C-S figure is not an offence, but it does invite follow-up questions. The more accurate your bookkeeping during the year, the less distance there is between the two numbers.
Step 3: Choose the Right Form
IRAS offers three Corporate Income Tax Returns, and the choice is driven by revenue and by what you are claiming [2].
| Form | Who can use it | What must be submitted |
| Form C-S (Lite) | Singapore-incorporated companies with annual revenue of S$200,000 or below that meet all Form C-S conditions | The form only |
| Form C-S | Singapore-incorporated companies with annual revenue of S$5 million or below | The form only |
| Form C | All other companies | Form, financial statements, tax computation and supporting schedules |
To qualify for Form C-S, a company must be incorporated in Singapore, have annual revenue of S$5 million or below, derive only income taxable at the prevailing 17% rate, and not be claiming any of the following in that YA [2]:
- Carry-back of current year capital allowances or losses
- Group relief
- Investment allowance
- Foreign tax credit and tax deducted at source
Expert Note: Filing Form C-S does not mean you can skip preparing financial statements and a tax computation. It means you are not required to submit them with the form. They must still be prepared, retained, and produced if IRAS requests them. Companies that mistake “not submitted” for “not needed” are the ones caught out when a query arrives.
Step 4: Prepare the Tax Computation
This is the actual work, and it sits between your accounts and your return. A tax computation reconciles accounting profit to chargeable income by adjusting for items treated differently under tax law:
- Add back non-deductible expenses — private motor vehicle costs, entertainment without a business purpose, fines, personal expenses routed through the company, and accounting depreciation.
- Claim capital allowances in place of depreciation on qualifying plant, machinery and equipment.
- Deduct allowable expenses that were wholly and exclusively incurred in producing the income.
- Apply unutilised items — losses and capital allowances carried forward, where the shareholding continuity test is satisfied.
- Account for approved donations to Institutions of a Public Character.
The accuracy of every line here depends entirely on the quality of your ledgers. This is why accounting services singapore and tax filing are best handled by the same team — a misclassified expense discovered in November is a reconstruction exercise, not a correction.
Step 5: Submit Through myTax Portal
All Corporate Income Tax Returns are filed electronically at mytax.iras.gov.sg.
Before you can file, confirm the Corppass authorisation is in place. The individual filing must be authorised for Corporate Tax Matters under the company’s Corppass account. Sorting this out in late November, when access issues take days to resolve, is a predictable and avoidable crisis.
The YA 2026 filing deadline is 30 November 2026 [3]. Companies filing through accounting software under IRAS’s Seamless Filing from Software (#SFFS) initiative have until 15 December 2026.
This deadline applies even if your company made a loss, and even if it did not carry on business during the financial year. Dormancy does not remove the obligation unless IRAS has granted a specific waiver. For the full deadline sequence, see our detailed guide to corporate income tax submission singapore.
Step 6: Check the Notice of Assessment and Pay
After your return is processed, IRAS issues a Notice of Assessment (NOA) setting out the tax payable. Payment is due within one month of the NOA date, regardless of any objection you intend to raise.
Review the NOA rather than filing it away. If the figures do not match your computation, there is a formal objection window, and acting inside it is far simpler than unwinding an assessment later.
Reliefs are applied by IRAS automatically from what you filed. For YA 2026, this includes the Corporate Income Tax Rebate, which was enhanced to 50% of corporate tax payable with total benefits capped at S$40,000, alongside the start-up or partial tax exemption your company qualifies for.
Your YA 2026 Filing Checklist
☑️ Basis period confirmed: Do you know which financial year maps to YA 2026 for your company?
☑️ ECI handled: Filed within three months of your financial year end, or waiver conditions clearly met?
☑️ Form selected: Have you confirmed against all four Form C-S exclusions, not just the revenue figure?
☑️ Computation prepared: Non-deductible expenses added back, capital allowances claimed, unutilised items applied?
☑️ Access ready: Is Corppass authorisation for Corporate Tax Matters in place well before 30 November?
File It Once, File It Right
Most corporate tax problems in Singapore are not disputes about the law. They are the result of filings assembled at speed from records that were never quite in order.
Since 1976, PC Lee & Co has prepared and filed corporate tax returns for Singapore SMEs as a practice of Chartered Accountants of Singapore. We prepare the tax computation, confirm which form applies, lodge your ECI and Form C-S or Form C on time, and check the Notice of Assessment when it arrives — with corporate tax services singapore handled by the same team that maintains your accounts.
If your financial year has just closed, speak to us now rather than in November. The earlier the computation is built, the more options remain open.
📞 Call us at: +65 6737 3710
✉️ Email: enquiries@pc-lee.com
📍 Visit: 545 Orchard Road, #10-06 Far East Shopping Centre, Singapore 238882
References
[1] Inland Revenue Authority of Singapore (IRAS). (2026). Estimated Chargeable Income (ECI) Filing. https://www.iras.gov.sg/taxes/corporate-income-tax/estimated-chargeable-income-(eci)-filing
[2] Inland Revenue Authority of Singapore (IRAS). (2026). Overview of Form C-S/ Form C-S (Lite)/ Form C. https://www.iras.gov.sg/taxes/corporate-income-tax/form-c-s-form-c-s-(lite)-form-c-filing/overview-of-form-c-s-form-c-s-(lite)-form-c
[3] Inland Revenue Authority of Singapore (IRAS). (2026). Corporate Income Tax Filing Season 2026. https://www.iras.gov.sg/taxes/corporate-income-tax/basics-of-corporate-income-tax/corporate-income-tax-filing-season-2026