The last quarter of the year is when most Singapore SMEs feel the squeeze. Finance teams are closing the books, sales are pushing for revenue, and at the same time directors are thinking about corporate income tax, IRAS deadlines, and cash flow.

Without a clear year-end corporate tax process, it is easy to miss an obligation or underestimate the final tax bill. That can lead to penalties, delayed assessments, and uncomfortable questions from shareholders and lenders.

This guide sets out a structured year-end corporate tax checklist for Singapore SMEs. It focuses on:

• How corporate income tax works in Singapore

• What to do at financial year end

• How to handle Estimated Chargeable Income (ECI)

• How to choose between Form C, Form C-S and Form C-S (Lite)

• How to build a proper tax computation and track IRAS deadlines

The goal is simple: help you move from reactive firefighting to a predictable, repeatable year-end tax process.

1. Start with the basics of corporate income tax in Singapore

Singapore operates a territorial, flat-rate corporate tax system. Most companies pay corporate income tax at 17% on their chargeable income, which is the final taxable amount after adjustments and exemptions.

If you need a concise overview of the rules, IRAS maintains a basic guide to corporate income tax for companies that explains general principles, filing obligations, and digital services.

For year-end planning, keep three ideas in mind:

1. Basis period: Tax is assessed on a preceding-year basis. Income for the financial year ending 31 December 2024 falls into Year of Assessment (YA) 2025.

2. Two main submissions: Most companies must submit an ECI early, then a full corporate income tax return (Form C, Form C-S or Form C-S Lite) for the relevant YA.

3. Documentation duty: IRAS expects companies to prepare and retain proper tax computations and schedules, even where simplified returns are allowed.

Everything in your year-end corporate tax checklist flows from these building blocks.

2. Confirm your financial year end and basis period

Before you touch any tax forms, lock in your dates.

• Financial Year End (FYE): The closing date of your financial year, for example 31 December or 30 June.

• Basis period: The financial year that feeds into a particular YA. Income for FYE 31 December 2024 is assessed in YA 2025.

At year end, check:

• Whether there has been any change in FYE that might split one long period across two YAs.

• Whether the first set of accounts for a new company covers more than 12 months, which may also require splitting income into two YAs.

If you are unsure how your basis period lines up with the corporate income tax filing season, IRAS publishes a dedicated page for the corporate income tax filing season 2025, including examples for different year ends.

A simple timeline that shows FYE, YA, ECI deadline and Form C / C-S deadline is an easy internal control to implement and avoids confusion later.

3. Close the books properly before you work on tax

Year-end corporate tax computations are only as reliable as the underlying numbers. Before anyone estimates ECI or drafts a tax return, the accounts should be closed and reviewed.

3.1 Complete core year-end accounting tasks

Key steps include:

• Bank reconciliations: Reconcile all bank accounts to statements and clear unexplained differences.

• Receivables and payables review: Identify long-outstanding invoices, potential bad debts and disputed balances.

• Inventory counts: For companies with stock, carry out a physical count and adjust to actual quantities.

• Accruals and prepayments: Record items such as accrued staff bonuses, audit fees, prepaid rent and insurance so income and expenses fall into the correct period.

• Director and shareholder balances: Reconcile loans and advances to directors or shareholders and consider whether interest should be imputed for tax purposes.

These adjustments determine your profit before tax, which is the starting point for the corporate income tax computation.

3.2 Review allowable and non-allowable expenses

For tax purposes, expenses must be wholly and exclusively incurred in the production of income to be deductible. Non-business, private, or capital items need to be added back in the tax computation.

Examples of expenses that are commonly non-deductible include:

• Fines and penalties

• Depreciation of fixed assets (capital allowances are used instead)

• Certain provisions that do not meet IRAS criteria

• Private portions of motor vehicle expenses

At year end, marking these items clearly in your ledger lets you convert accounting profit into chargeable income swiftly when you prepare the corporate income tax computation.

4. Prepare and file Estimated Chargeable Income (ECI)

Estimated Chargeable Income (ECI) is an estimate of your company’s taxable income for the YA. IRAS requires most companies to file ECI within three months from the end of their financial year.

You can find the detailed conditions, examples and FAQs on the Estimated Chargeable Income (ECI) filing page.

4.1 When you can skip ECI

A company is exempt from filing ECI for a particular YA if it meets both of these conditions:  

1. Annual revenue for the financial year is S$5 million or below, and

2. ECI for that YA is nil.

If your revenue exceeds S$5 million, or if there is any chargeable income, ECI still needs to be filed, even if the amount seems small.

4.2 Why ECI matters for year-end corporate tax

Treat ECI as an early warning system for cash flow and compliance. It helps with:

• Cash flow planning: Once ECI is accepted, IRAS will issue a Notice of Assessment and companies can often pay corporate income tax via GIRO instalments instead of a lump sum.

• Compliance risk control: Companies that ignore ECI risk estimated assessments and potential enforcement action if corporate income tax returns are also late.

As part of your checklist, assign responsibility for ECI to a named person or external tax agent, confirm the internal deadline, and track the filing status.

5. Decide between Form C, Form C-S and Form C-S (Lite)

All companies that carry on business or receive income must file a corporate income tax return each YA. The main forms are:

• Form C-S

• Form C-S (Lite)

• Form C

IRAS summarises the conditions and differences in its overview of Form C-S, Form C-S (Lite) and Form C.  

5.1 Form C-S

Form C-S is a simplified corporate income tax return for qualifying small companies. Key conditions include:  

• Company is incorporated in Singapore

• Annual revenue is S$5 million or below

• Only income taxable at the standard 17% rate

• No claims for items such as group relief, investment allowance or foreign tax credit

Companies filing Form C-S do not submit their tax computation and financial statements together with the return, but must have them ready and kept for inspection.

5.2 Form C-S (Lite)

Form C-S (Lite) is a further streamlined version for companies with annual revenue of S$200,000 or less that also meet the conditions for Form C-S. Fewer fields are required, which reduces preparation time for very small, straightforward entities.  

5.3 Form C

Companies that do not qualify for Form C-S or Form C-S (Lite) must file Form C. This requires submission of:

• Full tax computation

• Financial statements

• Supporting schedules and, where applicable, detailed claims for reliefs and incentives

A good year-end process will confirm eligibility early, then align the level of documentation with the complexity of the form to be filed.

6. Build a robust corporate income tax computation

Regardless of which form you file, IRAS expects a proper tax computation that reconciles your accounting profit to chargeable income.  

The IRAS page on preparing a tax computation sets out the structure and common adjustments.  

A typical computation will:

1. Start with profit before tax from your final accounts.

2. Add back non-deductible expenses, for example depreciation, private expenses, fines or non-qualifying provisions.

3. Deduct tax-allowable items, such as capital allowances on plant and machinery, and qualifying donations to approved institutions.  

4. Apply relevant tax exemption schemes, such as the partial tax exemption or start-up tax exemption (if conditions are met).  

5. Offset any unutilised losses or capital allowances brought forward, subject to shareholding and business continuity rules.

6. Arrive at chargeable income, which is subject to corporate income tax at 17%.

At year end, review whether your capital allowance schedule is current, whether any new fixed assets were missed, and whether there are losses that can be unlocked by meeting ownership requirements.

7. Track deadlines for year-end corporate tax filing

For YA 2025, IRAS has emphasised that companies must file their corporate income tax returns by 30 November 2025.

In practice, every year you should track:

• ECI filing deadline:

• Within three months from FYE, unless the ECI waiver conditions are met.

• Corporate income tax return deadline (Form C, C-S, C-S Lite):

• 30 November of the relevant YA for e-filing.

• Tax payment deadlines:

• As shown on the Notice of Assessment, or according to GIRO instalment arrangements.

A simple internal compliance calendar that covers corporate income tax, GST, ACRA annual return and payroll obligations makes it easier for directors to see what is coming due each quarter.

8. Plan for corporate tax payment, rebates and cash flow

Year-end corporate tax planning should include cash flow, not just compliance.

Useful points to consider:

• GIRO instalments: Companies that file ECI early and are on GIRO can usually spread corporate income tax over several monthly instalments, which reduces strain on working capital.

• Tax rebates and reliefs: For certain YAs, the government may grant corporate income tax rebates or cash grants through the Budget process. When these apply, they should be reflected in tax computations and cash flow forecasts.

• Dividend planning: Final dividends should be considered after estimating tax payable, so that distributions do not leave the business short of funds to pay corporate income tax.

A conversation between directors, finance and your tax advisor in the last quarter of the year can align expectations and avoid surprises when assessments are issued.

9. Avoid common year-end corporate tax mistakes

Several errors recur across SMEs and can be avoided with a systematic checklist:

• Assuming ECI is not required: Some companies skip ECI without confirming revenue and ECI conditions. IRAS systems will still show “Ready to File” even when an ECI waiver applies, so internal understanding is important.  

• Thinking dormant means “no obligations”: Dormant companies may still be required to file a corporate income tax return unless IRAS has granted a specific waiver.  

• Skipping tax computation for Form C-S filers: Form C-S reduces the fields you enter into myTax Portal, but IRAS still expects a full tax computation to exist in your files.  

• Misclassifying capital and revenue: Treating capital expenditure as a deductible expense, or vice versa, distorts both accounts and tax.

• Ignoring IRAS queries: Delayed or incomplete responses can escalate routine reviews into more detailed examinations of your corporate income tax affairs.

Including these items in your year-end review helps reduce the risk of penalties and additional tax assessments later.

10. Shift from year-end scramble to year-round governance

Although this article focuses on year-end corporate tax, the strongest SME finance functions treat tax as a continuous process.

Practical steps include:

• Quarterly reviews: Look at profitability, large adjustments and unusual items every quarter and flag potential tax issues early.

• Standardised documentation: Create clear folders for contracts, major invoices, bank documents and board resolutions, so that supporting documents for key tax positions are always easy to find.

• Accounting software that supports tax filing: IRAS encourages companies to use approved accounting software and provides guidance on using software to prepare Form C-S.  

• Clear internal responsibility: Decide who owns ECI, who owns the corporate income tax return, and when external advisors should be consulted.

Over time, this moves your year-end work from crisis mode to a controlled, predictable process with fewer surprises.

How ATHR can support your year-end corporate tax and corporate income tax filing

Many Singapore SMEs understand that corporate income tax is important, but do not have the resources to manage every step in-house, especially during peak year-end periods.

ATHR is a Singapore-based corporate service provider backed by over 40 years of professional experience through our group. We help SMEs, startups and regional groups manage their year-end corporate tax and ongoing compliance in a practical, structured way.

Our accounting and tax team can assist with:

• Year-end accounts closing: Finalising management accounts, performing reconciliations and posting year-end adjustments so that the numbers you file are accurate and defendable.

• Tax computations and ECI filing: Preparing detailed corporate income tax computations, identifying non-deductible expenses and capital allowances, and filing ECI within the required three-month window.

• Corporate income tax returns (Form C, Form C-S, Form C-S Lite): Determining eligibility for simplified forms, preparing supporting schedules, and filing your YA returns with IRAS by the 30 November deadline.

• Ongoing accounting and tax advisory: Providing monthly or quarterly bookkeeping, management reporting and tax input so that year-end corporate tax is the final step in a year-long process rather than a stressful event.

If you want your next year-end corporate tax cycle to be more controlled, more predictable and better aligned with your growth plans, expert support can make a material difference.

Book a call with ATHR today to explore our accounting and corporate income tax filing packages and see how we can help your business stay compliant with IRAS requirements while you focus on running and expanding your company.

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