Every active Singapore company must file an annual corporate tax return with the Inland Revenue Authority of Singapore (IRAS). There are two return forms — Form C-S and Form C — and choosing the wrong one is one of the most common compliance errors we see. Form C-S is the simpler form designed for small companies; Form C is the full return for everyone else.
This 2026 guide explains the eligibility criteria, the differences in disclosure, the new Form C-S (Lite) for the smallest companies, and how to decide which form your company should use this year of assessment (YA).
The Three Forms at a Glance
For YA 2026 (financial year ending in 2025), IRAS offers three corporate tax return forms:
- Form C-S (Lite): A streamlined version of Form C-S, available where annual revenue does not exceed S$200,000 and the Form C-S eligibility conditions are met. Only 6 fields to complete.
- Form C-S: A simplified income tax return for small qualifying companies. No financial statements or tax computation need to be submitted to IRAS, although these must still be prepared and retained.
- Form C: The full income tax return. Financial statements, tax computation, and supporting schedules must be submitted with the form.
The filing deadline for all three forms (for YA 2026) is 30 November 2026. The deadline applies regardless of the company’s financial year end.
Form C-S Eligibility (Who Can Use the Simplified Form?)
To file Form C-S, a Singapore company must satisfy all four of the following conditions for the YA in question:
- The company is incorporated in Singapore.
- The company’s annual revenue is not more than S$5 million.
- The company derives only income taxable at the prevailing corporate tax rate of 17% — no concessionary tax rate, no preferential incentive.
- The company is not claiming any of the following:
- Carry-back of capital allowances or losses.
- Group relief.
- Investment allowance.
- Foreign tax credit and tax deducted at source.
If any one condition is not met, the company must file Form C with full financial statements and tax computation.
Form C-S (Lite) Eligibility — For Singapore’s Smallest Companies
Form C-S (Lite) was introduced from YA 2020 to ease compliance for the smallest taxable companies. To qualify, your company must:
- Meet all the Form C-S conditions above, AND
- Have annual revenue of S$200,000 or less.
Form C-S (Lite) requires only 6 essential fields: revenue, adjusted profit/loss, estimated chargeable income, donations and a few others. It is by far the easiest corporate income tax return in Singapore and works well for new companies in their start-up years or holding companies with minimal activity.
When You Must File Form C
You must file Form C if any of the following apply:
- Annual revenue exceeds S$5 million.
- The company is not Singapore-incorporated (e.g. a Singapore branch of a foreign company).
- The company derives income subject to concessionary tax rates — for example, under the 13O or 13U family office incentives or a Pioneer / Development & Expansion incentive.
- The company is claiming carry-back relief, group relief, investment allowance, or foreign tax credit.
- The company has related-party transactions requiring transfer pricing documentation and reporting in the related party transaction (RPT) form.
Key Differences in What You Submit
| Item | Form C-S (Lite) | Form C-S | Form C |
|---|---|---|---|
| Annual revenue threshold | ≤ S$200,000 | ≤ S$5 million | No cap |
| Submit financial statements | No | No | Yes |
| Submit tax computation | No | No | Yes |
| Submit detailed P&L (Form C-S(L)) | No (6 fields only) | Required if revenue > S$500K | Not applicable |
| Group relief / foreign tax credit | Not allowed | Not allowed | Allowed |
| Time to complete (typical) | 15 minutes | 30 minutes | 2–4 hours |
Even if you file Form C-S or C-S (Lite), your company is still required to prepare and retain proper financial statements and tax computation for at least 5 years. IRAS can request these at any time during a tax review or audit.
The Filing Process Step-by-Step
Step 1: File the Estimated Chargeable Income (ECI)
Within 3 months of the end of the financial year, file the ECI — see our dedicated guide on ECI filing in Singapore. The ECI is separate from the Form C / C-S filing.
Step 2: Prepare financial statements
Even Form C-S filers must have proper financial statements prepared in accordance with the Singapore Financial Reporting Standards (SFRS) or SFRS for Small Entities. The accounts should be audited if your company exceeds the small company exemption thresholds under the Companies Act.
Step 3: Prepare the tax computation
Adjust accounting profit to tax-adjusted chargeable income — add back disallowable expenses (e.g. private motor car expenses, depreciation), deduct capital allowances and approved donations, apply partial tax exemption and the start-up exemption if eligible.
Step 4: File via myTax Portal
Log in to the myTax Portal using Corppass. Select the relevant form, complete the fields, and submit by 30 November.
Step 5: Pay the tax
IRAS issues a Notice of Assessment (NOA) after processing the return. Tax is due 1 month from the NOA date, although GIRO instalment plans of up to 10 months are commonly used.
Common Mistakes to Avoid
- Filing Form C-S when ineligible. If revenue exceeds S$5M or the company claims foreign tax credit, the return must be Form C. IRAS will reject the wrong form and the company may miss the 30 November deadline.
- Forgetting to add back private expenses. Director’s car expenses, private medical, and entertainment of a non-business nature must be added back to accounting profit.
- Missing capital allowance claims. Section 19 / 19A capital allowances are not automatic — they must be claimed in the tax computation. Missing them inflates taxable income.
- Late ECI filing forfeits the 10-month GIRO instalment plan. Always file ECI within 3 months of financial year end.
How Raffles Corporate Services Can Help
Our tax team prepares the full suite — accounts, tax computation, ECI and the Form C / C-S — for hundreds of Singapore companies every year. We assess Form C-S vs Form C eligibility at the start of each engagement so you file the right form first time, and we optimise the computation to ensure every eligible relief is claimed.
If you would like a fee proposal or a complimentary review of your prior year tax position, get in touch.
— The Editorial Team, Raffles Corporate Services