Choose the assessment year and understand filing status
Open corporate-tax filing through tax-agent login, enter the client’s tax reference and continue to the filing summary. New means the form is not yet completed; draft is saved work; pending approval awaits the approver’s formal IRAS submission. In this May 2026 edition, draft and pending forms are kept for 21 days or until 30 November, whichever is later. Select the correct assessment year; screenshot years are illustrations.
Revenue and form choice
Enter the client company’s revenue for the period. At S$200,000 or less, choose C-S Lite or C-S; above S$200,000 and up to S$5 million, the interface proceeds to C-S. Revenue entry is mandatory, but it is not the only eligibility condition. Complete the declarations and use Form C if the client fails the applicable conditions.
Part A: eligibility, reviewer and financial period
Both forms require responses to three qualifying-condition declarations. Companies that do not meet the conditions must use Form C. Declare whether an SCTP-accredited income-tax adviser or practitioner reviewed the return. If so, enter the reviewer’s name and membership number; where several accredited reviewers were involved, the guide allows details of one. Check and correct the pre-filled financial period, then continue. The portal saves information when moving forward; the draft-saving and cancellation controls allow work to be saved or the form choice revisited.
Part B: enter actual tax-adjustment figures
Amount fields initially show zero and must be replaced wherever the correct amount differs. A first financial period exceeding 12 months, or a change of financial year-end, can require figures for two assessment years; read the warning before continuing. Form C-S automatically computes specified adjusted-profit, rental-income, total-income and carried-forward balances. Lite similarly computes income totals and unused capital allowances, losses and donations to carry forward. Automatic calculation does not remove the need to supply correct source figures.
Pre-filled balances, donations and the YA 2026 note
Check unused capital allowances and losses brought forward against company records and use the company-declaration boxes for discrepancies. Donations brought forward, current donations and overseas donations are also pre-filled where IRAS has information. Current donation figures come from approved institutions or designated charities; the guide permits upward adjustments only for a company using a non-Singapore-dollar functional currency. Use the donation-detail view to inspect auto-included items, then close that tab to resume filing. From YA 2026, the guide allows qualifying PTIS donation deductions in the overseas-donation declaration, with the corresponding affirmative declaration at Item 19c for Form C-S or Item 12c for Lite.
Part C and additional reporting triggers
The revenue entered at form selection carries into the financial-statement section but can be corrected there; other zero-filled amounts must also be checked. Lite includes a non-taxable-income field from YA 2022. From YA 2023, declare any trading-stock appropriation for non-trade or capital purposes, or conversion of a non-trade/capital asset into trading stock; an affirmative answer requires the AC Reporting Form through document submission. From YA 2025, declare realised gains or losses from foreign-asset disposal. Complete the Enterprise Innovation Scheme fields only for qualifying claims; the guide identifies these fields from YA 2024, including relevant Form C-S tax-adjustment fields.
Review the estimate, then submit in the correct role
Review the confirmation page, correct mistakes and complete the declaration plus filer/contact details. Approvers submit directly to IRAS; preparers send the form for approval. Confirm the chosen action in the pop-up. The estimated tax shown is derived from the declaration and is not the final assessed amount. The CIT rebate cash grant is not reflected in that acknowledgement estimate; where applicable, it is accounted for in final tax payable on the Notice of Assessment.
Proof of filing and document version
Successful IRAS filing generates an acknowledgement number; an internal preparer handoff does not. Save or print the acknowledgement, or retrieve it from corporate-tax notices/letters. Use the next-client control to continue for another client, keeping each record separate. IRAS published this forty-page tax-agent guide on 5 May 2026. It explains both form workflows, rather than replacing the substantive tax rules behind each field.
Official source
This article independently explains the substantive contents of the official PDF, including the relevant conditions, procedures and annexes. The linked document remains the authoritative source for its original wording, and later changes should be checked separately.
Read the official PDF ↗