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Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →Singapore companies normally have two separate corporate-income-tax filing points each year. Estimated Chargeable Income (ECI) is generally due within three months after the financial year end. The annual Form C-S, Form C-S (Lite) or Form C return is due on 30 November; for Year of Assessment (YA) 2026, the deadline is 30 November 2026. Both obligations are handled electronically through IRAS’s myTax Portal, and an ECI waiver does not cancel the annual return.
Keep the evidence behind the filing—not just the online declaration—for at least five years from the relevant YA. That includes financial statements, tax computations, schedules, invoices and receipts, bank statements and other transaction records. Filing an ACRA annual return is a separate legal obligation and does not satisfy the IRAS tax return.
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The Singapore corporate-tax calendar
Work from two dates rather than treating “corporate tax” as one annual task:
| Filing | Normal deadline | What it covers |
|---|---|---|
| Estimated Chargeable Income (ECI) | Within three months after the company’s financial year end, unless an applicable waiver or specific exemption applies | An estimate of the company’s chargeable income for the financial period |
| Annual corporate-income-tax return | 30 November every year; YA 2026 is due 30 November 2026 | Form C-S, Form C-S (Lite) or Form C, with the information and documents required for the company’s filing category |
The ECI deadline follows your financial year end (FYE), while the annual return uses the fixed 30 November deadline for that YA. Put both dates in the company’s compliance calendar as soon as the accounts close.
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ECI: what to file and when
Deadline calculation
Count three months from the last day of the company’s financial year. For example, a company whose FYE is 31 December normally files ECI by 31 March of the following calendar year. A different FYE produces a different three-month date.
When a waiver applies
IRAS may allow an ECI waiver or another specific exemption in circumstances set out in its rules. Confirm that the company actually qualifies before treating ECI as waived. A waiver only affects the ECI filing; it does not remove the annual Form C-S, Form C-S (Lite) or Form C obligation due on 30 November.
Information to assemble
Use the closing accounts and tax adjustments to arrive at the ECI figure. Keep the working papers that explain the estimate so that the eventual annual return can be reconciled to the underlying records. If the estimate changes materially as the accounts are finalised, retain both the original ECI working and the final tax computation.
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The annual return: Form C-S, Form C-S (Lite) or Form C
Form C-S and Form C-S (Lite)
These are simplified declarations for companies that meet IRAS’s requirements for the relevant form. “Simplified” describes the declaration, not the company’s record-keeping burden. The company must still prepare and retain the financial statements, tax computation, supporting schedules and evidence for the figures reported.
For a Form C-S or Form C-S (Lite) filing, prepare:
- Audited or unaudited financial statements, as applicable.
- The tax computation and supporting schedules.
- The Section 19B intellectual-property writing-down-allowance declaration, when applicable. This declaration is filed with the return.
- Other supporting documents that substantiate income, deductions, allowances and claims. These are retained and supplied to IRAS if requested.
Form C
Form C is the fuller filing route and requires a wider attachment set. In addition to the financial statements and tax computation, prepare:
- Form IRIN 301.
- A detailed profit-and-loss statement.
- Relevant claim forms, such as group-relief or applicable research-and-development forms.
- A revised tax computation where a loss-carry-back claim or previously unreported income issue requires one.
- The Section 19B declaration, where applicable.
- Other supporting documents requested by the filing requirements or needed to substantiate the return.
Use the form category that IRAS permits for the company. Do not choose Form C-S or Form C-S (Lite) merely because the company’s accounts are straightforward; eligibility is determined by the applicable IRAS conditions. If those conditions are not met, prepare Form C and its fuller attachments.
Form C-S versus Form C: practical differences
| Issue | Form C-S / Form C-S (Lite) | Form C |
|---|---|---|
| Declaration | Simplified declaration for an eligible company | Fuller corporate-tax return |
| Financial statements and tax computation | Prepare and retain audited or unaudited financial statements, tax computation and supporting schedules | Prepare and submit the required financial statements and tax computation in the electronic attachment set |
| Detailed profit-and-loss statement | Not listed as a separate filing attachment in the Form C-S preparation list | Required |
| Form IRIN 301 | Not listed as a separate Form C-S attachment | Required |
| Claim forms and special schedules | Retain relevant evidence and provide it if IRAS requests it | Attach relevant claim forms, including applicable group-relief or R&D forms |
| Section 19B declaration | File with the return when applicable | File with the return when applicable |
| Revised computation for loss carry-back or previously unreported income | Use the applicable IRAS process if the issue arises | Prepare a revised tax computation when required |
The table describes the preparation and attachment distinctions identified by IRAS; the company must still retain the underlying evidence for either route.
Documents to prepare before filing
Financial statements
Have the relevant audited or unaudited financial statements ready. They provide the accounting starting point for the tax computation and support the income, expense, asset and liability figures in the return.
Tax computation and schedules
The tax computation bridges accounting profit or loss to chargeable income. Keep schedules showing each material adjustment, allowance, deduction, loss and claim. A reviewer should be able to trace every significant number from the return to the accounts and then to source records.
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Source evidence
Organise invoices, receipts, contracts, payroll or other expense support, sales records, purchase records, bank statements and transaction listings. These records are not replaced by checking a box in myTax Portal; they are the evidence IRAS may request later.
Special declarations and claims
Check whether the Section 19B intellectual-property writing-down-allowance declaration applies. For Form C, identify any group-relief, R&D or other claim forms and prepare them before opening the electronic submission. If a loss-carry-back or previously unreported income issue changes the computation, prepare the revised version required for that case.
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- Confirm the company’s FYE and YA. Use the FYE to calculate the ECI date and the YA to identify the 30 November annual-return deadline.
- Select the permitted return. Decide between Form C-S, Form C-S (Lite) and Form C using the company’s eligibility under IRAS rules.
- Finalise the accounts and tax computation. Reconcile the accounting records to the tax schedules and resolve open claims or adjustments.
- Prepare the attachment set. For Form C, include the financial statements, detailed profit-and-loss statement, tax computation and other required supporting documents. Include the applicable declarations and claim forms.
- Log in to myTax Portal. The return is filed electronically through myTax Portal by an authorised Corppass approver.
- Upload readable files. Form C supporting documents should be in PDF format. Scanned pages must be clear, and attachments should use at least 11-point font.
- Review and submit. Check the company details, YA, ECI-related information, income, deductions, claims and attachments before the authorised approver submits the return.
- Preserve the submission record. Keep the filed return, acknowledgement and the exact supporting files with the tax working papers for the required retention period.
Record-keeping: what to retain and for how long
Minimum retention period
IRAS requires a company to keep records for at least five years from the relevant Year of Assessment. The retention set includes source documents, accounting records and schedules, bank statements and other transaction records connected with the business. The five-year test is tied to the YA, not simply to the date on which a document was created.
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How the YA rule works
For IRAS’s example, a company with a December year end for YA 2023 keeps its 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. Record the destruction date in the company’s retention schedule so that files are not deleted early.
After striking off
A person responsible for a struck-off company must retain its books and papers for at least five years after dissolution. Striking off therefore does not immediately end the record-keeping obligation.
What a defensible file looks like
- The filed ECI and annual return, including acknowledgements.
- Audited or unaudited financial statements.
- Tax computations, reconciliation schedules and any revised computations.
- Invoices, receipts, contracts and other source documents for income and expenses.
- Bank statements and transaction-level accounting records.
- Form C attachments, IRIN 301, detailed profit-and-loss statements and relevant claim forms.
- Section 19B declarations and evidence supporting the underlying allowance or claim.
- Notes explaining unusual transactions, estimates, corrections and correspondence relevant to the filing.
IRAS says proper records help a company understand profit or loss, make decisions, reduce filing effort and answer IRAS queries. Accounting software can support digital transaction management and tax compliance; IRAS maintains an Accounting Software Register Plus (ASR+) for software that meets its stated requirements.
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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteACRA annual return is not the IRAS tax return
Companies have a separate annual-return filing obligation with ACRA. Completing that filing does not submit the corporate-income-tax return to IRAS, and an IRAS filing does not replace the ACRA annual return. Track the two agencies, portals and deadlines separately, with separate completion evidence.
Late filing and enforcement risk
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 measures such as composition or summons when deadlines are missed. The practical response is to start the accounts and tax-computation work well before 30 November and escalate missing records or unresolved claims instead of allowing the filing to lapse.
A workable annual process
- At financial-year end: close the books, reconcile bank accounts and identify missing source documents.
- Within the next three months: prepare and file ECI unless a confirmed waiver or exemption applies.
- During accounts finalisation: complete the financial statements, tax computation, schedules and any special declarations or claims.
- Before 30 November: select the correct return, assemble the electronic attachments and obtain Corppass approval.
- After submission: archive the return, acknowledgement, attachments and working papers together.
- Each year: review the retention schedule and keep every file until at least five years after the relevant YA, or five years after dissolution for a struck-off company.
This sequence prevents the most common compliance mistake: treating an ECI waiver, a Form C-S declaration or an ACRA annual return as if it eliminated the other obligations.
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