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Singapore companies normally have two separate corporate-income-tax obligations each year: file Estimated Chargeable Income (ECI) within three months after the financial year end, then submit Form C-S, Form C-S (Lite) or Form C by 30 November. For Year of Assessment (YA) 2026, the annual return deadline is 30 November 2026. An ECI waiver does not cancel the annual return. Keep the financial evidence behind the filing for at least five years from the relevant YA.
Singapore corporate tax deadlines at a glance
The deadlines below apply to the ordinary annual filing cycle described by the Inland Revenue Authority of Singapore (IRAS). A company may have a different filing position if a specific exemption or waiver applies, but it should not assume that one waiver covers every obligation.
| Obligation | Due date | What the company submits or does |
|---|---|---|
| Estimated Chargeable Income (ECI) | Within three months after the financial year end | Submit ECI electronically unless an ECI waiver or specific exemption applies. |
| Annual corporate-income-tax return | 30 November every year | File Form C-S, Form C-S (Lite) or Form C, as applicable. |
| YA 2026 annual return | 30 November 2026 | Complete the relevant Form C-S or Form C filing through myTax Portal. |
| Tax-record retention | At least five years from the relevant YA | Keep source documents, accounting records, schedules, bank statements and transaction records that support the return. |
ECI: three months after your financial year end
ECI is the company’s estimate of its chargeable income for the financial period. The filing window is measured from the end of that financial year, not from 30 November. For example, a company whose financial year ends on 31 December normally has three months after that date to file its ECI, unless IRAS grants or recognises an applicable waiver or exemption.
Because the ECI deadline moves with each company’s year end, put it on the compliance calendar as soon as the financial year closes. Do not wait for the annual Form C-S or Form C deadline to address ECI.
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Annual Form C-S, Form C-S (Lite) or Form C: 30 November
The annual return is due on 30 November every year. IRAS specifies 30 November 2026 for YA 2026. This date remains separate from the company’s ECI date, even when the company filed an ECI waiver.
An ECI waiver is not an annual-return waiver
A company that qualifies for an ECI waiver still has to submit the annual Form C-S, Form C-S (Lite) or Form C unless IRAS separately says otherwise. Treat the waiver as applying only to the ECI obligation covered by its terms.
Where and how to file
Corporate-income-tax returns are filed electronically through myTax Portal. The submission must be made by an authorised Corppass approver. Arrange the approver access before the deadline so a completed return is not held up by an account or authorisation problem.
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- Confirm the filing year and due dates. Identify the relevant YA, the financial year end used for ECI, and the 30 November annual-return deadline.
- Collect the accounting and tax records. Finalise the financial statements, tax computation, schedules and any claim-specific evidence before opening the online return.
- Choose the correct return. Use the Form C-S or Form C-S (Lite) route only when the company meets the applicable IRAS conditions. Otherwise prepare Form C and its fuller attachments.
- Sign in to myTax Portal with the authorised Corppass approver. Check that the company profile and filing authority are correct.
- Enter, review and submit. Reconcile the figures in the online declaration to the financial statements and tax computation, attach documents required for Form C, and submit before 30 November.
- Keep the submission evidence. Save the acknowledgement and the exact documents submitted with the records for that YA.
Do not treat an ACRA filing as a substitute for this process. ACRA’s annual-return filing and IRAS’s corporate-tax filing are separate obligations administered by different authorities.
Which return should you use?
IRAS provides three annual return formats: Form C-S, Form C-S (Lite) and Form C. The simplified forms reduce the information entered in the declaration, but they do not remove the need to prepare reliable accounts and supporting evidence.
| Feature | Form C-S / Form C-S (Lite) | Form C |
|---|---|---|
| Purpose | Simplified annual declaration for companies that meet the applicable IRAS conditions. | Fuller corporate-income-tax return for companies that do not use the simplified route or that must provide the detailed Form C information. |
| Financial statements | Prepare audited or unaudited financial statements and retain them for IRAS if requested. | Prepare financial statements and submit them in soft copy with the return. |
| Tax computation | Prepare the tax computation and supporting schedules; retain them and provide them if IRAS requests them. | Submit the tax computation in soft copy with the return. |
| Detailed profit-and-loss statement | The simplified declaration does not require the Form C detailed profit-and-loss attachment described by IRAS. | Submit a detailed profit-and-loss statement and Form IRIN 301. |
| Claims and special schedules | Prepare any applicable claim support and the Section 19B declaration where relevant; retain supporting evidence. | Attach relevant claim forms, such as group-relief or applicable R&D forms, and the Section 19B declaration where relevant. |
| Other supporting documents | Keep the underlying documents and supply them if IRAS asks. | Provide the supporting documents required for the Form C submission in soft copy. |
What the simplified forms do—and do not—simplify
Form C-S and Form C-S (Lite) are simplified declarations, not permission to skip the accounting work. The company still needs financial statements, a tax computation, schedules and documentary support that explain how the figures were produced. The principal difference is what must be entered or attached with the return versus what can be retained for a possible IRAS request.
When Form C is the practical route
Form C has a fuller attachment set. In addition to the financial statements and tax computation, prepare Form IRIN 301, the detailed profit-and-loss statement and any relevant claim forms. IRAS also refers to revised tax computations where a loss-carry-back claim or previously unreported income issue applies. Include the Section 19B intellectual-property writing-down-allowance declaration when it is applicable.
The available evidence does not establish a universal revenue threshold or other single test that determines every company’s eligibility for Form C-S or Form C. Check the current IRAS conditions for the company’s facts rather than selecting a form based only on size or past-year practice.
Documents to prepare before the annual return
Financial statements
Prepare the company’s audited or unaudited financial statements for the relevant period. They should agree with the accounting ledger and provide the starting point for the tax computation. For Form C, IRAS requires the statements in soft copy.
Tax computation and schedules
The tax computation bridges accounting profit or loss and the amount used for corporate-tax purposes. Keep the calculation and every supporting schedule, including workings for adjustments, allowances and claims. Form C filers submit the tax computation in soft copy; Form C-S and Form C-S (Lite) filers prepare and retain it for production if IRAS requests it.
Section 19B declaration
If the company claims the Section 19B intellectual-property writing-down allowance, prepare the required declaration. The declaration is filed with the return when applicable, regardless of whether the company is using a simplified or full form. Retain the evidence supporting the claim.
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Form C-specific attachments
A Form C package may include all of the following, depending on the company’s circumstances:
- Financial statements in soft copy.
- The detailed profit-and-loss statement.
- Form IRIN 301.
- The tax computation and supporting schedules.
- Relevant claim forms, including group-relief or applicable R&D forms.
- A revised tax computation where a loss-carry-back or previously unreported income issue requires one.
- The Section 19B declaration where the allowance is claimed.
- Other supporting documents requested by IRAS or needed to substantiate the figures.
Evidence behind every number
Maintain the invoices and receipts, accounting records and schedules, bank statements and other transaction records that explain income, business expenses and purchases. A return that can be submitted online but cannot be supported by source documents is not a complete compliance file.
Electronic submission requirements for Form C
IRAS requires Form C financial statements, the detailed profit-and-loss statement, the tax computation and other supporting documents to be provided in soft copy. Use PDF files. Scanned documents should be clear enough to read, and attachments should use at least 11-point font.
- Open each PDF after scanning to confirm that every page is legible and in the correct order.
- Check that schedules reconcile to the figures entered in the return.
- Use descriptive file names so the company can identify the document and YA later.
- Keep the final files exactly as submitted, together with the myTax Portal acknowledgement.
Record-keeping requirement: at least five years
IRAS requires a company to retain records for at least five years from the relevant Year of Assessment. The retention set must explain the company’s income, business expenses and purchases. It includes source documents, accounting records and schedules, bank statements and other transaction records connected with the business.
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How the five-year period is counted
The clock is tied to the relevant YA, not simply to the date on which an invoice was issued or the financial year ended. IRAS’s example for a company with a December year end and YA 2023 keeps the records through 31 December 2027. For a non-December year end, calculate the end date by reference to the relevant YA in the same way; do not assume that five calendar years after the financial year end is the correct date.
Struck-off companies
A person responsible for a struck-off company must retain the company’s books and papers for at least five years after dissolution. Striking the company off the register does not immediately eliminate the record-keeping duty.
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Organise records so they can be retrieved
Use a folder or accounting-system structure that separates each YA and links the return to its source evidence. Keep the final financial statements, tax computation, schedules, claim forms, invoices and receipts, bank statements, transaction records and filing acknowledgement together. IRAS encourages accounting software and maintains an Accounting Software Register Plus (ASR+) for software that supports digital transaction management and tax compliance. The key requirement is not a particular product; it is that the records remain complete, accurate and retrievable.
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These filings answer different regulatory questions and must be scheduled separately.
| Filing | Authority | What it does | Does it replace the other filing? |
|---|---|---|---|
| Annual return | Accounting and Corporate Regulatory Authority (ACRA) | Maintains the company’s statutory corporate information with ACRA. | No. It does not satisfy the IRAS corporate-income-tax return. |
| ECI | IRAS | Reports estimated chargeable income within three months after the financial year end, unless a waiver or exemption applies. | No. It does not replace the annual Form C-S, Form C-S (Lite) or Form C return. |
| Form C-S, Form C-S (Lite) or Form C | IRAS | Submits the annual corporate-income-tax declaration by 30 November. | No. It does not replace the ACRA annual return. |
Put all three checkpoints on the company’s calendar where applicable: the ECI date based on the financial year end, the IRAS annual return date of 30 November, and the separate ACRA annual-return date.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Penalties for late or missing filing
For YA 2026, IRAS states that late filing or non-filing may result in penalties of up to S$5,000. The Form C-S/Form C guidance also refers to enforcement actions such as composition or summons for missed deadlines. A late filing can therefore create both a financial exposure and an escalation risk.
If the company discovers that a deadline has been missed, submit the outstanding return and supporting information as soon as possible, preserve evidence of the submission, and address any IRAS notice promptly. Do not assume that an ECI waiver or a completed ACRA filing explains the missed annual IRAS return.
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- At financial-year end: close the ledger, reconcile bank accounts, gather invoices and receipts, and identify the three-month ECI date.
- During the ECI preparation window: prepare the estimate and file it through myTax Portal unless the company has a valid ECI waiver or specific exemption.
- While preparing the annual return: finalise audited or unaudited financial statements, complete the tax computation and schedules, and decide whether the simplified form conditions are met.
- For a Form C filing: prepare Form IRIN 301, the detailed profit-and-loss statement, relevant claim forms, revised computations where applicable, and soft-copy PDFs that meet the legibility and font requirements.
- Before 30 November: have the authorised Corppass approver review and submit the return in myTax Portal. Leave time to correct rejected files or authorisation issues.
- After submission: store the acknowledgement and the complete evidence file under the relevant YA retention folder.
- Each year: keep the records until at least five years from the relevant YA, and extend the process for a struck-off company to at least five years after dissolution.
Common mistakes and how to correct them
Mistake: treating the two IRAS deadlines as one
Fix: track ECI from the financial year end and the annual Form C-S/Form C deadline on 30 November as separate calendar events.
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Mistake: assuming an ECI waiver ends all filing duties
Fix: keep the annual return in the calendar unless IRAS has separately confirmed that obligation does not apply.
Mistake: choosing a simplified form without checking conditions
Fix: verify the current IRAS eligibility conditions and retain the full accounts and tax computation even when Form C-S or Form C-S (Lite) is appropriate.
Mistake: submitting Form C without its detailed package
Fix: use a Form C checklist covering Form IRIN 301, detailed profit-and-loss, tax computation, financial statements, relevant claim forms, revised computations where needed, the Section 19B declaration where applicable and other supporting documents.
Mistake: keeping only the online declaration
Fix: retain source documents and transaction evidence, not just the confirmation page. IRAS’s five-year rule applies to the records that explain the figures.
Mistake: confusing ACRA compliance with tax compliance
Fix: assign separate owners and due dates for the ACRA annual return, ECI and the IRAS annual tax return.
Quick Recap
Key takeaways for YA 2026
- File ECI within three months after the financial year end unless a specific waiver or exemption applies.
- File Form C-S, Form C-S (Lite) or Form C by 30 November; YA 2026 is due on 30 November 2026.
- Use myTax Portal with an authorised Corppass approver.
- Prepare financial statements, tax computations and supporting schedules even when using a simplified form.
- For Form C, include the detailed profit-and-loss statement, Form IRIN 301 and applicable claim or revised-computation documents.
- Retain the evidence behind the filing for at least five years from the relevant YA.
- Keep ACRA’s annual return separate from IRAS tax filings.
- Late or missing YA 2026 filing may attract penalties of up to S$5,000.
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