Corporate Income Tax Return: Forms, Filing, and Deadlines

Filing a corporate income tax return in Belgium is mandatory for all resident companies and Belgian branches of foreign businesses. The return must be submitted annually using the official corporate income tax return form via the Biztax platform.

As a rule, the corporate income tax return due date falls on the last day of the seventh month after the end of the financial year. For financial years ending between 31 December 2024 and 28 February 2025, the deadline is exceptionally extended to 30 September 2025. 

A complete and timely business tax return ensures compliance with Belgian tax law, which is administered by the Federal Public Service Finance and enforced through strict deadlines and documentation standards.

What is a Corporate Income Tax Return?

A corporate income tax return Belgium is the official declaration through which companies report their taxable income to the Belgian tax authorities. Resident companies are taxed on their worldwide profits, while non-resident companies with a Belgian establishment are taxed only on Belgian-source income. 

The return must be filed annually using the standard corporate income tax return form, submitted via the Biztax platform. It includes financial statements, disallowed expenses, deductions, and other relevant tax data. Filing an accurate business tax return ensures that the correct amount of corporate income tax is assessed and paid under Belgium’s tax legislation.

Why is Corporate Income Tax Filing Important?

Timely and accurate filing of a corporate income tax return is not just a legal formality, it safeguards your business from penalties and unnecessary scrutiny.

Here’s why it matters:

• Avoids ex officio assessment: If the return is not filed on time, the tax authorities may issue an estimated assessment, and the burden of proof lies with the company.
• Limits audit exposure: Filing within the deadline restricts the tax authority's right to revise your return to a standard period (generally four years from 1 January of the assessment year).
• Prevents penalties: Late or incorrect returns may trigger tax increases, administrative fines, or even criminal penalties in serious cases.
• Ensures legal compliance: Submission of the correct corporate income tax return form through Biztax is a statutory obligation for both resident and non-resident entities.
• Supports financial transparency: A properly filed business tax return reflects the company’s financial health and helps maintain its credibility with stakeholders.

Step-by-Step Guide to Filing Your Corporate Income Tax Return

Filing a Corporate Income Tax (CIT) return in Belgium involves multiple steps, from identifying the correct tax year to calculating tax payments and filing via Biztax. Here's a detailed walkthrough to help businesses stay compliant:

1. Determine Your Taxable Period

The taxable period is linked to the financial year of your company:

• If your financial year ends on 31 December 2024, the tax year is 2025.
• If your financial year ends on 30 June 2024, the tax year is 2024.

This classification is important for applying the correct rules and deadlines.

2. Understand Your Filing Deadline

For companies closing their books between 31 December 2024 and 28 February 2025, the filing deadline is 30 September 2025. In all other cases, the deadline is the last day of the seventh month following the end of the financial year. If this date falls on a weekend or public holiday, the deadline shifts to the next working day. Extensions may be granted for serious reasons or force majeure, but they must be requested and justified.

3. Prepare the Tax Return

Your corporate tax return is based on the accounting income shown in your filed annual accounts, Adjustments required by tax law (e.g., disallowed expenses, exempted income) and the net taxable profit after adjustments and exemptions (Articles 181, 182, 216–219c CIR 92).

4. Calculate the Tax Due

Standard CIT rate: 25% (in force from tax year 2021 onwards, for financial years starting on or after 1 January 2020). Certain sectors may qualify for reduced rates or full exemptions (e.g., voluntary sector, education). The tax base includes total net income, including distributed profits.

5. Make Advance Tax Payments (Optional but Recommended)

Advance tax payments help avoid CIT surcharges. For a financial year ending 31 December 2025 (tax year 2025), quarterly due dates are: 10 April 2025, 10 July 2025, 10 October 2025, and 20 December 2025.

If a due date falls on a weekend/public holiday, payment is due on the next working day. Payments give rise to tax credits: Q1: 12%, Q2: 10%, Q3: 8%, and Q4: 6%. 

Credits exceeding the surcharge won’t affect your final tax computation, but you may request a refund or carry them forward. 

6. File Electronically via Biztax

The CIT return must be submitted electronically through the Biztax application (mandatory for most companies). Paper filing is only allowed in exceptional cases (e.g. IT limitations). You must provide a signed declaration explaining the reason and send it to your tax office. This does not extend your filing deadline.

7. Pay the Tax Due

Payment is due within two months after the issuance of the tax assessment (unless exceptions apply). Late payments are subject to 4% annual interest, non-cumulative.

8. For Foreign Companies: Register with FPS Finance

If your company was formed under foreign law and operates in Belgium, you must contact the tax office to create a tax file, this is not done automatically. Belgian companies are registered automatically via the Crossroads Bank for Enterprises (CBE).
 

Important Corporate Income Tax Deadlines

To ensure timely filing and avoid penalties, it's essential to keep track of corporate tax deadlines based on your company’s balance sheet date. Below is a summary of key dates:

Who must follow this?
This filing schedule applies to all legal entities, regardless of:

• Method of filing (electronic or paper)
• Legal situation (normal operations, liquidation, etc.)
• Tax type (Corporate Income Tax, Income Tax on Legal Entities, or Non-Resident Company Tax)

Conclusion

Filing your Corporate Income Tax return in Belgium is more than a compliance obligation, it's a legal requirement tied to strict deadlines, detailed financial reporting, and accurate declarations. Whether you’re a Belgian or foreign company operating in Belgium, understanding your tax year, respecting the filing deadlines, and using the correct submission method (Biztax) is crucial to avoid penalties, interest, or tax surcharges. Always refer to the official calendar and guidelines to ensure your company stays on track.

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