Corporate Tax in Singapore: The Filings Your Company Owes IRAS, in the Order They Fall Due

Last updated: 6 September 2026 · Author: SBC Team

Singapore taxes company profits at a flat 17% of chargeable income. Two filings carry that tax to the Inland Revenue Authority of Singapore (IRAS). The first is the Estimated Chargeable Income (ECI), due within three months of your financial year end. The second is the annual income tax return — Form C-S, Form C-S (Lite) or Form C — due on 30 November in the Year of Assessment that follows. Two obligations, two deadlines, and the gap between them is where most first-time founders get lost.

This guide covers both filings in the order they fall due, the basis period concept that sets the timing, how chargeable income differs from the profit in your accounts, and what happens if a filing is late. Every figure is traceable to IRAS. Thresholds and rebates change at Budget, so confirm the current position on the page linked in each section before you file.

The Filings at a Glance

Four obligations sit on a Singapore company’s annual calendar. Three are IRAS filings. The fourth belongs to the Accounting and Corporate Regulatory Authority (ACRA), the companies registrar, and gets confused with the tax return because both land in the same part of the year.

The ACRA annual return and the IRAS tax return are not substitutes. Filing one does not discharge the other.

Basis Period and Year of Assessment

This is the concept founders get wrong, and it explains why the tax return falls due almost a year after the accounts close.

Your basis period is the financial year whose profits are being taxed. The Year of Assessment (YA) is the year in which IRAS assesses and charges tax on those profits. Income earned in a financial year is assessed in the following calendar year, so YA 2026 taxes the financial year that ended in 2025.

A worked example. Your company closes its books on 31 December 2025.

• Basis period: 1 January 2025 to 31 December 2025.
• Year of Assessment: YA 2026.
• ECI due: 31 March 2026, three months after the financial year end.
• Form C-S due: 30 November 2026.

Move the year end and the ECI date moves with it. A company closing on 30 June 2025 also sits in YA 2026, files ECI by 30 September 2025, and still files its return by 30 November 2026. One more wrinkle applies to new companies: a first set of accounts may run past twelve months, and where that period straddles two YAs the profits are apportioned across both. The rules are in the IRAS basic guide to corporate income tax.

Filing 1: Estimated Chargeable Income

ECI is your own estimate of chargeable income for the Year of Assessment, filed before the audited numbers are final. You file it at myTax Portal using Corppass, the government’s corporate digital identity system, and whoever files must be authorised as an Approver for Corporate Tax. Report the estimate before any start-up or partial exemption, because IRAS applies those automatically. The deadline is three months from your financial year end, and it stands whether or not the IRAS notification reaches you.

When the ECI Filing Is Waived

You do not need to file ECI when both of these are true for the Year of Assessment:

• Annual revenue is S$5 million or below.
• The ECI is nil.

Both conditions, not either. A company with S$10 million of revenue and nil ECI still files. A company with S$5 million of revenue and S$100,000 of ECI still files. You self-assess the waiver, and there is nothing to submit to IRAS if you qualify. Check the current criteria on the IRAS ECI filing page before relying on it.

Why Filing Early Is Worth Money

IRAS issues a Notice of Assessment once it processes the ECI, and a company on GIRO can pay that assessment in monthly instalments instead of a single sum. How many instalments you get depends on how quickly you filed.

Two conditions attach. The company must be Singapore-registered and on GIRO, and it must file by the 26th of the qualifying month. If there is no GIRO arrangement for corporate tax yet, apply at least three weeks before filing, since it has to be approved before the payment due date. These tiers are administrative, so confirm them on the ECI filing page.

Filing 2: The Annual Income Tax Return

The return reports actual chargeable income for the Year of Assessment and is due on 30 November. Revenue and what you are claiming decide which of three forms you file.

Four claims disqualify a company from Form C-S in the Year of Assessment they are made:

• Carry-back of current year capital allowances or losses.
• Group relief.
• Investment allowance.
• Foreign tax credit and tax deducted at source.

Income taxed at a concessionary rate or exempted under an incentive also pushes you to Form C. One-tier tax exempt Singapore dividends and specified foreign-sourced income exempt under section 13(8) of the Income Tax Act 1947 are the exceptions. Confirm the revenue thresholds and conditions in force on the IRAS Form C-S and Form C overview before choosing a form.

You file even when the company made no money. A loss-making company files. A company with no income files. The return attaches to the company, not to its profitability.

Chargeable Income Is Not Accounting Profit

The 17% rate applies to chargeable income, which is the profit in your accounts after tax adjustments. Three adjustments account for most of the difference a first-time filer meets.

Non-Deductible Expenses

An expense is deductible only if it is incurred wholly and exclusively in producing income and is not capital in nature. Accounting depreciation, private and domestic expenses, fines, and the running costs of private S-plated cars are added back to profit.

Capital Allowances Replace Depreciation

You cannot deduct the depreciation in your accounts. You claim capital allowances on qualifying fixed assets instead, which is the tax system’s own way of writing an asset down. Low-value and certain prescribed assets can be written off faster than the standard schedule, and private cars attract no capital allowance at all. Current options are on the IRAS capital allowances page.

Unutilised Losses Carried Forward

Trade losses and capital allowances you could not use in a loss-making year carry forward indefinitely, subject to conditions. The main one is the shareholding test: the same shareholders must hold at least 50% of the shares on both relevant dates, comparing the year the loss arose against the year you want to use it. Capital allowances carry a second test, which is that the company still carries on the same trade. A founder who sells a majority stake between a loss year and a profit year can lose the relief, so model it before a funding round closes. Worked examples are on the IRAS page for unutilised capital allowances and trade losses.

If you would rather not build the tax computation yourself, our tax and accounting services cover the cycle from bookkeeping through to filing.

Exemptions and Rebates Before You Reach 17%

Two reliefs sit between chargeable income and the tax you pay. Qualifying new companies get the Start-Up Tax Exemption for their first three Years of Assessment, and everyone else gets the Partial Tax Exemption. IRAS applies both automatically. We cover the qualifying tests, the bands and the effective rates in our guide to the Start-Up Tax Exemption.

Rebates sit on top and are announced at Budget, so they change year to year. For YA 2026 IRAS has published an enhanced Corporate Income Tax Rebate of 50% of tax payable, a cash grant for active companies that made CPF contributions for at least one local employee, and a cap on the combined benefit. Read the parameters on the IRAS rate, rebates and exemption schemes page before assuming a rebate applies to your year.

What to Keep, and for How Long

Companies filing Form C-S or Form C-S (Lite) do not submit financial statements or a tax computation with the return. They still prepare both and produce them on request. Keep the following for at least five years from the relevant Year of Assessment:

• Source documents — invoices issued and received, receipts, vouchers, contracts.
• Accounting records and schedules, including the fixed asset register behind capital allowance claims.
• Bank statements for every company account.
• The tax computation and financial statements for each Year of Assessment.

Five years is the rule, published on the IRAS record keeping requirements page, and records may be kept electronically. For a company in its third year, that means year one’s paperwork is still live.

If You File Late, or Not at All

Missing either filing has the same first consequence. IRAS estimates the number for you, issuing an estimated Notice of Assessment based on previous years’ income or other information available to it, and the estimate may assume your income grew. Two things follow that founders rarely expect.

• The estimated tax is payable within one month of the Notice of Assessment. It is payable even if you disagree and have filed an objection. If the assessment is later revised, IRAS refunds the excess.
• The instalment benefit is gone. A company assessed on an estimate pays the full amount, not ten monthly deductions.

For a late or missing return, IRAS may also offer to compound the offence rather than prosecute, issue a notice to the company’s director under section 65B(3) of the Income Tax Act 1947, or summon the company and its officers to court. Composition amounts, late payment penalties and the sequence of recovery actions are published on the IRAS page for late filing or non-filing of corporate income tax returns. Check it for the current amounts.

Objecting to an Assessment

If you disagree with an assessment, file a Notice of Objection within two months of the date of the Notice of Assessment, using the Revise/Object to Assessment service at myTax Portal.

An objection against an estimated assessment only works if you file the missing paperwork with it: the tax return, the financial statements and the tax computation. Submit the objection without them and the estimated assessment is not revised. Pay the assessed amount while the objection is under review, because the payment obligation and the objection run in parallel.

Dormant Companies Still File

A dormant company carried on no business and had no income for the whole basis period. Dormant describes activity. It is not an exemption from filing.

A dormant company files by 30 November each year, unless IRAS has granted a waiver of return submission on application. The filing is light, since the Form for Dormant Company asks for two essential fields and no financial statements. ACRA obligations continue in parallel, including the annual return. Details are on the IRAS dormant companies page.

Paying After the Notice of Assessment

The Notice of Assessment is the bill, and tax is payable within one month of its date unless the company qualifies to pay by instalments. No Notice of Assessment is issued where a company files a nil ECI, because there is nothing to pay yet. GIRO is what unlocks instalments, and the arrangement has to be approved before the payment due date. If the chargeable income in your return comes out higher than the ECI you declared, you pay the difference within one month of the revised Notice of Assessment. If it comes out lower, IRAS refunds the excess automatically, though a large gap may prompt a question about how the estimate was reached. Payment modes are listed on the IRAS payment page.

Frequently Asked Questions

What is the corporate tax rate in Singapore?
A flat 17% of chargeable income, applying to both local and foreign companies. Chargeable income is accounting profit after tax adjustments, and after the start-up or partial tax exemption. Any Corporate Income Tax Rebate announced at Budget applies to the tax payable after that.

What is the difference between ECI and Form C-S?
ECI is your estimate of chargeable income, filed within three months of your financial year end so IRAS can assess tax early. Form C-S is the actual annual return for the Year of Assessment, due 30 November. Filing ECI does not replace the return, and filing the return does not excuse a missed ECI.

Do I have to file ECI if my company made no profit?
Not if your annual revenue is S$5 million or below and your ECI is nil. Both conditions have to hold. A company with revenue above that threshold files even when the ECI is nil. Confirm the current threshold on the IRAS ECI filing page before relying on the waiver.

When is the corporate tax return due in Singapore?
30 November of the Year of Assessment, which is the calendar year after your basis period ends. A company with a 31 December 2025 year end is in YA 2026 and files by 30 November 2026. That date does not shift with your financial year end, unlike the ECI deadline.

What happens if I miss the filing deadline?
IRAS may issue an estimated Notice of Assessment based on prior years’ income. The estimated tax is payable within one month even if you object, and no instalment plan is given. IRAS may also offer to compound the offence, or take further recovery action against the company and its directors.

Does a dormant company need to file a tax return?
Yes, by 30 November each year, unless IRAS has granted a waiver on application. The Form for Dormant Company requires only two fields and no financial statements. The ACRA annual return obligation continues separately.

If you want the basis period, the ECI deadline and the right return form settled before your next year end, our tax and accounting services cover bookkeeping, the tax computation, and filing with IRAS.