When is the Belgian corporate tax return due?
The return is due by the last day of the 7th month after the financial year-end. For a 31 December year-end that is 30 September. It is filed electronically on Biztax.
Finn does your books in Belgium
AccountsOS runs full accounting for Belgium businesses, tax, deadlines and invoicing, in plain English. Ask Finn about yours, no signup needed.
Detailed Explanation
## When is the Belgian corporate tax return due?
The corporate income tax return must be filed by the last day of the 7th month following the financial year-end. For financial years ending between 31 December and 28 February, the deadline is fixed at 30 September.
For example, a company with a 31 December 2025 year-end must file by 30 September 2026. If the deadline falls on a Saturday, Sunday or public holiday, it moves to the next working day.
## How to file
The return is filed electronically on Biztax, reached through the MyMinfin portal run by FPS Finance.
## Early filing
A company that files by 28 August for a December year-end gets priority refund processing. Refunds are typically paid by the end of December. This matters when advance payments have been higher than the final tax.
## What goes with the return
The return builds on the annual accounts. The company approves its accounts at the General Assembly and then files them with the National Bank of Belgium within 30 days of approval. The accounts filing is a separate deadline from the tax return.
## How AccountsOS helps
AccountsOS creates the deadline from your year-end and reminds you. Finn prepares the profit figures and the tax estimate. AccountsOS does not connect to Biztax. You or your accountant submits the return there.
Source: https://finance.belgium.be/en/E-services/biztax/deadline-filing-returns
Real-World Examples
December year-end
A company with a 31 December 2025 year-end files on Biztax by 30 September 2026.
Refund expected
A company expects a refund and files by 28 August 2026. It receives priority processing, typically paid by the end of December.
Deadline on a weekend
When the deadline falls on a weekend or public holiday, it moves to the next working day.
Common Mistakes to Avoid
- Waiting until the last day when a refund is expected
- Confusing the tax return date with the annual accounts filing date
- Assuming the weekend extension applies to quarterly VAT, which it does not
- Forgetting to check the SME rate conditions before filing
Frequently Asked Questions
What is the date for a 31 December year-end?
30 September of the following year.
Where do I file?
On Biztax through MyMinfin.
What if the date is a weekend?
It moves to the next working day.
Is there a benefit to filing early?
Yes. Filing by 28 August for a December year-end speeds up refunds.
Does AccountsOS submit the return?
No. You or your accountant submits it on Biztax.
Practical Tips
- Put 28 August in the calendar if you expect a refund
- Finalise the accounts well before the deadline
- Check the SME conditions and the Notional Interest Deduction before you file
- Keep the Biztax receipt with your records
Ask Finn your Belgium accounting questions
Finn knows FPS Finance (SPF Finances / FOD Financiën) rules and your specific business numbers. Get instant answers in plain English.
Try free for 14 days