Singapore Corporate Tax Filing Deadlines 2026

TL;DR — Key 2026 Deadlines at a Glance

Source: IRAS 2026 tax calendar. Always confirm current deadlines at iras.gov.sg.

For many entrepreneurs, tax season is the most dreaded time of the year. Between managing your business, your team, and your customers, tracking multiple filing deadlines across IRAS and ACRA can feel overwhelming especially when the consequences of missing one are financial penalties, not gentle reminders. The good news: getting a head start on your company tax return deadline for the year can help you be prepared, so you won’t have to be flustered when the deadlines are nearing.

This guide covers every key corporate tax filing deadline in Singapore for 2026, the rules behind each one, the applicable tax rates and exemptions, and exactly how to file — so you can go into the year with full clarity.

What Is Corporate Tax Filing in Singapore?

Corporate tax filing in Singapore is the annual process by which every company incorporated or registered here declares its chargeable income and pays the applicable tax to the Inland Revenue Authority of Singapore (IRAS). Singapore taxes corporate profits at a headline rate of 17%, though most SMEs pay significantly less after partial tax exemptions.

Filing is not optional and not conditional on whether your company made a profit. Even loss-making companies must file. IRAS uses the filing to establish your tax position, issue your Notice of Assessment, and determine whether any tax is payable, refunded, or carried forward.

There are two distinct filing obligations most SMEs need to manage:

• ECI (Estimated Chargeable Income): A preliminary estimate of your taxable profit, filed within 3 months of your financial year end.
• Form C-S / C: The full corporate income tax return, filed by 30 November each year for the preceding financial year.

Both are mandatory for most companies. Missing either triggers late-filing penalties under the Income Tax Act.

Who Needs to File Corporate Tax in Singapore?

Every company incorporated in Singapore — including those that are dormant or making losses — must file a corporate tax return with IRAS each year. There is no threshold below which filing becomes optional.

The only meaningful distinction is which form you file:

• Form C-S — For companies with annual revenue of S$5 million or below and straightforward tax affairs (no capital allowances carried forward, no foreign income, no losses claimed from related companies).
• Form C-S (Lite) — A simplified version of Form C-S for companies with revenue of S$200,000 or below.
• Form C — For all other companies, including those with revenue above S$5 million or more complex tax positions.

Newly incorporated companies are not exempt. If your company was incorporated mid-year, your first ECI filing is still due within 3 months of your first financial year end.

The Complete 2026 Corporate Tax Deadlines Calendar

Estimated Chargeable Income (ECI) — Rolling 3-Month Deadline

ECI is a preliminary estimate of your company’s taxable income for a given financial year. IRAS requires you to file it within 3 months of your financial year end.

Who is exempt from ECI filing? IRAS grants ECI waivers to companies that meet both conditions: annual revenue of S$5 million or below and ECI of zero (i.e. no taxable profit). If your company qualifies, you still must file Form C-S or C by 30 November.

Why ECI matters: If you miss the deadline, IRAS issues an estimated Notice of Assessment based on their own estimate of your income which you must pay until you file and successfully object.

Form C-S / C-S (Lite) / C — 30 November 2026

All companies — regardless of financial year end must file their full corporate income tax return by 30 November 2026 for Year of Assessment (YA) 2026. IRAS processes all corporate income tax returns through myTax Portal exclusively. Paper filing is not accepted.

GST Filing Deadlines — Monthly or Quarterly

GST-registered companies must file a GST return (Form F5) and pay any GST due within one month of the end of each accounting period.

• 31 January 2026 — GST return for companies with FY ending December
• 30 April 2026 — GST return for companies with FY ending March
• 31 July 2026 — GST return for companies with FY ending June
• 31 October 2026 — GST return for companies with FY ending September

From 1 April 2025, IRAS mandated InvoiceNow e-invoicing for newly GST-registered businesses. If your company registered for GST after that date, you must now transmit invoice data via the Peppol network. Read our full guide to InvoiceNow compliance in Singapore to understand what this means for your GST process.

IR8A — 1 March 2026

Employers must submit IR8A forms — reporting each employee’s total employment income for calendar year 2025 — to IRAS by 1 March 2026. This deadline also covers commission e-submissions.

Companies with 5 or more employees must participate in the Auto-Inclusion Scheme (AIS) and submit IR8A data electronically through myTax Portal. Under AIS, your employees’ income is automatically included in their personal tax returns without them needing to enter it manually.

Annual Return (ACRA) — 5 or 7 Months After Financial Year End

While not a tax filing, the ACRA Annual Return runs in parallel and carries its own penalties. Non-listed private companies must file within 7 months of their financial year end. Listed companies have 5 months. Late filing attracts ACRA penalties separate from any IRAS penalties.

What Are Singapore’s Corporate Income Tax Rates and General Tax Exemptions?

Singapore’s corporate income tax rate is a flat 17% on chargeable income. In practice, most SMEs pay far less than this after applying IRAS’s partial tax exemption schemes.

Standard Partial Tax Exemption (for companies in operation 3+ years)

Start-Up Tax Exemption (first 3 years of incorporation)

Qualifying new companies incorporated in Singapore receive a more generous exemption:

To qualify for the start-up exemption, your company must be incorporated in Singapore, be a tax resident of Singapore, and have no more than 20 shareholders — with at least one individual shareholder holding a minimum of 10% of shares. Investment holding companies and property development companies are excluded.

In practice, what this means for most SMEs: A company earning S$200,000 in its first year pays tax only on S$25,000 (the non-exempt portions after 75% and 50% relief), resulting in a tax bill of around S$4,250 before any further deductions a far cry from the headline 17%.

Note: These figures are illustrative. Always verify your actual tax position against IRAS’s tax calculator or consult your accountant before treating any computation as final.

How Do I File Corporate Tax in Singapore?

To file corporate tax in Singapore, follow these steps:

1. Log in to myTax Portal using your company’s CorpPass. You can file the tax return yourself, or authorise a staff member or third-party service provider in CorpPass to file on your behalf. You or any authorised person must verify identity through SMS OTP or OneKey Token.
2. Select the correct filing form. Click on “Corporate Tax” in the menu bar, then select “File ECI” or “File Form C-S/C” depending on which deadline you are meeting.
3. Follow IRAS’s guided instructions to complete the filing. For ECI, you enter your estimated chargeable income for the financial year. For Form C-S or C, you enter your full income, deductions, and tax computation.
4. Submit your return through the portal. IRAS will confirm receipt and generate a submission reference.

Note: All corporate tax filing happens exclusively through myTax Portal (mytax.iras.gov.sg). IRAS does not accept paper returns.

What Happens After You File?

By 31 May of the following year, IRAS issues your Notice of Assessment (NOA) after reviewing your company’s tax returns. The NOA states your company’s final tax liability and gives you the opportunity to raise an objection if you disagree with IRAS’s assessment.

If you accept the NOA and no objection is raised, you must pay the corporate tax due within 30 days of the NOA date. Acceptable payment methods include interbank GIRO, cheque, telegraphic transfer, and internet banking.

What Happens If You Miss a Corporate Tax Deadline?

IRAS treats late filing seriously. Missing a deadline does not result in a warning — it triggers automatic consequences.

Late ECI filing: IRAS raises an estimated Notice of Assessment based on its own estimate of your taxable income. You must pay based on that estimate, then file your ECI and formally object. The process takes time and creates a cash flow problem if IRAS overestimates your position.

Late Form C-S / C filing: IRAS issues a Composition Amount (financial penalty) under Section 94 of the Income Tax Act. Repeat non-compliance can result in prosecution.

Late GST filing: A 5% late payment penalty applies immediately on unpaid GST. After 60 days, an additional 2% per month applies, up to a maximum of 50% of the unpaid amount.

Late IR8A submission: Enforcement action may follow under the Income Tax Act.

The 4 Most Common Corporate Tax Filing Mistakes Singapore SMEs Make

1. Treating ECI and Form C-S as the same filing. They are not. ECI is a preliminary estimate filed within 3 months of your financial year end. Form C-S is the full return filed by 30 November. You must file both separately.

2. Assuming the ECI exemption applies automatically. The waiver requires both conditions: revenue of S$5 million or below and zero ECI. A company with no profit but revenue above S$5 million must still file ECI — the figure is simply zero, but the filing is mandatory.

3. Missing the GIRO deadline distinction. GIRO plan holders have an earlier ECI deadline than non-GIRO payers — for example, 26 March instead of 31 March for a December FY end. If you pay via GIRO and miss the 26th, IRAS treats it as a late filing even though the calendar deadline is five days later.

4. Treating collected GST as working capital. GST you collect from customers belongs to the government. Companies that draw on GST receipts for operating expenses and scramble at quarter-end create a recurring compliance and cash flow problem. File and pay on time, every quarter.

How Can Grof Help With Corporate Tax Filing in Singapore?

Managing Singapore’s corporate tax calendar — ECI, Form C-S, GST returns, IR8A, and ACRA filings — across multiple deadlines each year is a material compliance burden for any SME founder or finance manager. One missed filing does not produce a reminder; it produces a penalty.

Key takeaways:

• Every Singapore company must file corporate tax with IRAS — profit, losses, and dormancy do not exempt you.
• ECI is due within 3 months of your financial year end. GIRO holders have an earlier deadline.
• Form C-S or C is due by 30 November 2026 for YA 2026.
• The start-up tax exemption reduces effective tax significantly for qualifying companies in their first three years.
• GST returns are due within one month of each accounting period end.
• IR8A and commission e-submissions are due 1 March 2026 for 2025 employment income.

Grof’s corporate secretarial and accounting team tracks your full compliance calendar, prepares your tax computations, and files directly with IRAS and ACRA — so you focus on running your business, not chasing deadlines. Speak to Grof’s team about corporate tax compliance in Singapore.

Frequently Asked Questions