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Singapore companies file their annual corporate income tax return electronically in IRAS myTax Portal. First obtain Corppass authorization for “Corporate Tax (Filing and Applications),” then sign in with Singpass, select the correct Form C-S (Lite), Form C-S or Form C, attach or retain the required records, submit by 30 November, and save the acknowledgement. ECI is a separate estimate normally due within three months after the financial year end.
What you are filing, and when
IRAS requires an annual Corporate Income Tax Return from companies, even when there is no tax payable. The return is filed electronically as Form C-S (Lite), Form C-S or Form C. The annual deadline is 30 November every year. This deadline is separate from Estimated Chargeable Income (ECI), which is an estimate generally due within three months after the company’s financial year end. ECI is not a substitute for the annual Form C-S/Form C return.
IRAS’s 2026 guidance states that Form C-S, Form C-S (Lite) and Form C must be filed by 30 November to avoid enforcement actions such as composition or summons. Check the live IRAS notice for the relevant Year of Assessment (YA), particularly if your company uses approved accounting software that may qualify for an extension.
Choose the correct IRAS form
Your revenue is an initial screening point, not the only eligibility test. Use the form that matches all of IRAS’s conditions for the company and the YA.
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| Form | Who may use it | What is submitted | Preparation considerations |
|---|---|---|---|
| Form C-S (Lite) | Companies with annual revenue of $200,000 or below, subject to IRAS’s other qualifying conditions. | A shorter declaration in myTax Portal. | IRAS indicates a direct filing normally takes at least 10 minutes. Keep the financial statements and tax computation in case IRAS requests them. |
| Form C-S | Qualifying Singapore-incorporated companies with annual revenue of $5 million or below, income taxed at the prevailing 17% rate, and the other conditions specified by IRAS. | A simplified electronic return; supporting records are generally retained rather than uploaded with the form. | Direct filing normally takes at least 10 minutes. Confirm every eligibility condition, not just revenue. |
| Form C | Companies that do not meet the simplified-form conditions, or that otherwise must provide the full return. | The full electronic return plus financial statements, a detailed profit-and-loss statement, tax computation and supporting documents as clear PDF files. | IRAS indicates a direct filing normally takes at least 30 minutes. Allow additional time to prepare and check attachments. |
The $200,000 and $5 million figures are annual-revenue thresholds in IRAS’s 2026 guidance. The Form C-S threshold also requires, among other conditions, that the company’s income be taxed at the prevailing 17% corporate income tax rate. If any condition is uncertain, do not select a simplified form merely because revenue is below a threshold; use the eligibility guidance or have your tax agent confirm the position.
When Form C is the safer route
Form C is the full return for a company outside the simplified-form conditions. It is also the route to consider when the information required for a simplified declaration is not available or when a specific IRAS condition is not met. The portal may require more detailed figures and PDF attachments, so collect the records before opening the return.
Set up access before filing
An employee, director or tax agent cannot file solely by having a personal Singpass. The person must be authorized for the company in Corppass with the “Corporate Tax (Filing and Applications)” role, and the authorization must include the appropriate Approver access for filing. Have the company’s Unique Entity Number (UEN) or Entity ID and the authorized user’s Singpass ready.
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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11- Confirm the company account. Verify the legal entity and UEN or Entity ID that will appear in the return. A wrong entity selection can attach a filing to the wrong company.
- Assign the Corppass role. The company’s Corppass administrator authorizes the employee or external tax agent for “Corporate Tax (Filing and Applications)” and grants the required Approver permission.
- Check the user can act for the entity. The proposed filer should sign in to Corppass and confirm that the company is available before the filing deadline. Resolve role or entity errors with the company’s Corppass administrator first.
- Prepare Singpass. The authorized person uses Singpass to enter IRAS services. Do not share Singpass credentials; an agent should receive delegated Corppass access instead.
Authorization is a prerequisite, not an optional convenience. If a staff member can open the portal but cannot see the company or submit the return, the usual first check is whether the correct Corppass service and Approver role were granted.
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Prepare the records and files
Prepare the accounting figures before starting the online form. At minimum, reconcile the company’s financial statements to the tax computation and identify the figures that the selected form asks for. Keep a copy of every source document and the final submitted values.
Records for Form C-S (Lite) and Form C-S
Form C-S and Form C-S (Lite) filers should retain their financial statements and tax computation. IRAS may request these records later, even though the simplified filing normally does not require them to be uploaded with the return. Retain the working papers that explain adjustments from accounting profit to taxable income, along with the evidence supporting those adjustments.
Attachments for Form C
Form C filers attach all items IRAS requires for the return: the financial statements, detailed profit-and-loss statement, tax computation and supporting documents. Upload clear PDF files. When reducing attachment size, IRAS advises using at least 11-point font and 100 dpi black-and-white scans. Check every PDF after compression to ensure numbers, notes and signatures remain legible.
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- Open each PDF before upload and confirm that every page is present and in the correct order.
- Keep an uncompressed master copy in the company’s records even if a smaller PDF is uploaded.
- Make sure the figures in the attachments agree with the values entered in myTax Portal.
File directly in myTax Portal
The standard route is the IRAS myTax Portal at mytax.iras.gov.sg. Start early enough to correct authorization or attachment problems before 30 November.
- Sign in. Open myTax Portal and authenticate with Singpass. Select the company represented by the authorized Corppass role, checking the UEN or Entity ID.
- Open corporate tax filing. Choose the service for the Corporate Income Tax Return and the applicable YA. Confirm that the return is for the intended company and period.
- Select the form. Choose Form C-S (Lite), Form C-S or Form C only after checking all eligibility conditions. If the company does not qualify for a simplified form, select Form C.
- Enter the tax information. Transfer the prepared figures carefully from the approved financial statements and tax computation. Recheck decimal places, signs and any adjustments before moving on.
- Upload Form C documents. If filing Form C, attach the required PDFs. Use the portal’s validation messages to identify missing or unreadable files, then replace the file and validate again.
- Review the declaration. Read the declaration, verify the company identity, YA, form type, figures and attachments, and ensure the person submitting has authority to approve the filing.
- Submit once. Complete the electronic declaration and submit. Wait for the confirmation page rather than closing the browser immediately.
- Save evidence. Download or print the acknowledgement, note the submission date and reference, and store it with the source records and final PDFs.
IRAS says a Form C-S or Form C-S (Lite) submission usually takes at least 10 minutes and a Form C submission at least 30 minutes. Those are minimum preparation times for the direct online process, not a promise that a complex return will finish within that period.
Use approved accounting software when eligible
Eligible Form C-S companies may submit through qualifying accounting software under IRAS’s Simplified Form for Supporting (SFFS) arrangement. For YA 2023 through YA 2027, IRAS automatically extends the filing deadline by 15 days for qualifying software submissions: from 30 November to 15 December. The extension applies to qualifying Form C-S filings made through the approved software route, not automatically to every electronic filing or to Form C.
Before relying on the extension, verify that the software and company meet the current SFFS conditions and that the submission is actually transmitted through the qualifying route. Keep the software-generated confirmation as well as the IRAS acknowledgement. If eligibility or transmission is uncertain, plan to meet the normal 30 November deadline through myTax Portal.
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Authorize a tax agent or other third party
A company may authorize a tax agent or another third party through Corppass. The delegation lets the agent act for the company without using the company’s Singpass credentials. The company remains responsible for ensuring the return is complete, accurate and filed on time.
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- Have the company’s Corppass administrator grant the agent access to “Corporate Tax (Filing and Applications)” with the permissions needed to prepare and submit the return.
- Give the agent the financial statements, tax computation, supporting documents and any internal filing instructions through a secure channel.
- Agree who reviews the final figures and who receives the acknowledgement. The company should retain a copy of the submitted return and all source records.
- Check that the agent’s authorization remains active for the relevant YA and has not expired or been revoked before submission.
Using an agent changes who performs the keystrokes, not the statutory deadline. A company that delegates filing still needs an internal review and evidence that the return was submitted.
Check the filing after submission
Keep the acknowledgement with the tax computation, financial statements, uploaded PDFs and any correspondence. IRAS states that filing status can be checked through myTax Portal or the IRAS Bot from three working days after filing. If the status is not visible immediately, retain the acknowledgement and check again after that period.
Use a simple internal close-out checklist:
- The acknowledgement identifies the correct company and YA.
- The form type matches the company’s eligibility assessment.
- All required Form C attachments were accepted.
- The submitted figures match the approved tax computation.
- The next ECI due date and the following annual return deadline are recorded separately.
Deadlines: annual return versus ECI
| Obligation | What it is | Normal timing | Important distinction |
|---|---|---|---|
| ECI | An estimate of chargeable income filed with IRAS. | Generally within three months after the financial year end. | It is not the final annual Form C-S/Form C return. |
| Form C-S (Lite), Form C-S or Form C | The annual Corporate Income Tax Return for the YA. | 30 November each year. | Every company must meet the applicable annual filing requirement unless IRAS has granted a specific waiver. |
| SFFS Form C-S submission | A qualifying simplified filing sent through approved accounting software. | For YA 2023–YA 2027, IRAS provides a 15-day automatic extension, from 30 November to 15 December, when the SFFS conditions are met. | The software route and eligibility conditions must be satisfied; do not assume the extension applies to a portal filing. |
IRAS publishes ECI dates by financial year end and updates filing guidance. Record the company’s actual financial year end and verify the current date in the relevant IRAS notice rather than treating the ECI window as the annual return deadline.
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What happens if the return is late
Late or missing filing can trigger several IRAS actions. IRAS may issue an estimated Notice of Assessment, which is payable within one month. It may offer composition, issue a Section 65B(3) notice to a director, or issue a court summons. These consequences are in addition to the need to submit the overdue return.
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A dormant company is not automatically exempt from e-filing. It must file the dormant-company form unless IRAS has granted a waiver. If a return is overdue, complete the Corppass authorization and submit it through myTax Portal as soon as possible, then retain the acknowledgement and any payment or correspondence records.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Troubleshoot common filing problems
The company is missing from the portal
Check that the user signed in with the intended Singpass identity and that Corppass lists the correct UEN or Entity ID. Ask the company’s Corppass administrator to confirm authorization for “Corporate Tax (Filing and Applications)” and the Approver role. Re-entering figures will not fix an entity or role problem.
The portal rejects a simplified form
Recheck every Form C-S or Form C-S (Lite) condition, including the relevant revenue threshold, Singapore-incorporation requirement where applicable, and the 17% prevailing-rate condition for Form C-S. If a condition is not met, prepare Form C instead of repeatedly attempting to force a simplified return.
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A Form C PDF will not upload
Open the file locally, confirm it is a readable PDF, remove accidental blank or corrupted pages, and reduce the scan size while preserving at least 11-point text and 100 dpi black-and-white quality as IRAS advises. Upload the corrected file and verify that the portal marks it as accepted.
The acknowledgement was not saved
Check the portal’s filing history and the filing status through myTax Portal or the IRAS Bot after three working days. If the return shows as submitted, save the acknowledgement or reference then. Keep browser or email evidence only as a supplement; the portal acknowledgement is the primary filing record.
The deadline has passed
Do not wait for a reminder. Confirm authorization, prepare the correct form, file the overdue return in myTax Portal and review any Notice of Assessment, composition offer, director notice or summons issued by IRAS. Deal with payment and response dates separately from the filing itself.
Quick Recap
Which route should you choose?
| Route | Best fit | Preparation time indicated by IRAS | Attachments | Authorization | Deadline treatment |
|---|---|---|---|---|---|
| Direct myTax Portal, Form C-S (Lite) | Companies meeting the Lite conditions, including annual revenue of $200,000 or below. | At least 10 minutes for the online form, excluding accounting preparation. | Retain financial statements and tax computation; upload requirements depend on portal instructions. | Corppass Approver for Corporate Tax (Filing and Applications). | 30 November each year. |
| Direct myTax Portal, Form C-S | Qualifying Singapore-incorporated companies with annual revenue of $5 million or below and the other Form C-S conditions. | At least 10 minutes for the online form. | Retain financial statements and tax computation. | Corppass Approver authorization. | 30 November each year. |
| Direct myTax Portal, Form C | Companies that do not qualify for a simplified form. | At least 30 minutes for the online form, plus document preparation. | Financial statements, detailed profit-and-loss statement, tax computation and supporting PDFs. | Corppass Approver authorization. | 30 November each year. |
| Qualifying SFFS accounting software | Eligible Form C-S filers already using approved software. | Varies by software and accounting readiness. | Data is transmitted through the software route; retain source records and confirmations. | Company and software permissions must be correctly configured. | For YA 2023–YA 2027, a 15-day extension to 15 December applies when all SFFS conditions are met. |
| Tax agent or other authorized third party | Companies that want an agent to prepare or submit on their behalf. | Depends on the agent and complexity of the return. | Provide the agent with the records required for the selected form; retain copies internally. | Delegate through Corppass; never share Singpass credentials. | The company remains responsible for the applicable deadline. |
A practical filing calendar
- At financial year end: note the ECI due date, which is generally three months after the year end, and begin closing the accounts.
- During tax preparation: complete the tax computation, determine the correct form and gather Form C PDFs if required.
- Before November: test Corppass access, verify the UEN or Entity ID and resolve any role issue while there is time to obtain help.
- Before 30 November: submit the annual return directly, through an eligible SFFS route or through an authorized agent. Do not rely on the SFFS extension unless eligibility and transmission are confirmed.
- After submission: save the acknowledgement and check the filing status after three working days if needed.
- After filing: retain the source records and monitor IRAS correspondence, including any Notice of Assessment or request for supporting documents.
Key points to verify before you click Submit
- The company and YA shown in myTax Portal are correct.
- The selected form is supported by all applicable IRAS conditions, not revenue alone.
- ECI has been treated as a separate obligation.
- Form C attachments are complete, readable PDFs using IRAS’s scan guidance where files are reduced.
- The submitter has Corppass Approver authorization for “Corporate Tax (Filing and Applications).”
- The annual deadline is 30 November, unless a confirmed SFFS extension applies for the relevant YA.
- The acknowledgement and underlying records are stored where the company can retrieve them.
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