Before you start

National register number
A determination of whether you are a Belgian tax resident
itsme or an eID card reader, to use MyMinfin
Your employer's assessment of whether the inbound taxpayer regime applies

Step-by-step

1
Establish whether you are a Belgian tax resident
Residence turns on where your home and centre of economic interests sit, with entry in the population register creating a rebuttable presumption. Residents are taxed on worldwide income; non-residents only on Belgian-source income, on a different return.
OnlineWho: You
2
Raise the inbound taxpayer regime at contract stage
Under the inbound taxpayer regime the employer can pay part of your gross remuneration as tax-free expense reimbursement. The employer applies within a short window after employment begins, and if the window closes the regime is unavailable for that engagement. This is a conversation for the offer, not the first payslip.
Via employerWho: Your employerAt hiring
3
Know the brackets and where 50% begins
For income year 2026 the rates are 25%, 40%, 45% and 50%, with the top rate from roughly €48,000 of taxable income and a basic tax-free allowance around €11,180. Employee social security of 13.07% is deducted from gross before income tax is calculated, so budgeting from a gross figure overstates what arrives.
OnlineWho: You
4
Check your specific commune's surcharge before you sign a lease
The additional communal tax is a percentage of the income tax you owe, voted by each commune and published annually by FPS Finance. Liège charges 8.0% for assessment year 2026 — against 7.0% in Antwerp, 6.5% in Ghent and 4.9% in the City of Brussels — and neighbouring Walloon communes differ from it and from each other. In an agglomeration of separate municipalities this is a live decision when you choose an address, and it is where you are registered on 1 January that fixes the rate for the year.
OnlineWho: You
5
Check the pre-filled proposal rather than ignoring it
Many employees receive a proposed simplified return instead of a blank one. It still has to be checked and corrected — deductions the administration cannot see, such as childcare, pension savings, charitable gifts or a foreign account, will simply be missing. Accepting a wrong proposal by silence is on you.
OnlineWho: YouLate April to mid-July
6
Declare foreign accounts, insurance and property
Belgian residents must report foreign bank accounts to the National Bank's central point of contact and declare foreign life insurance and foreign immovable property in the return, with foreign property valued on the same cadastral basis as Belgian property since the 2021 reform. In a city an hour from Germany, Luxembourg and the Netherlands, this catches a lot of people who kept an account at home.
OnlineWho: You

Documents you’ll need

National register number and itsme or eID reader
Annual payslip summary (fiche 281.10)
Records of foreign accounts, insurance policies and property
Certificates for pension savings, childcare and mortgage deductions
Any inbound taxpayer regime confirmation

Things most newcomers don’t know

Liège's 8.0% surcharge is the highest of Belgium's major cities, and the neighbours are not uniform.

The additional communal tax is levied on the tax you already owe, not on income, and each commune votes its own rate. For assessment year 2026 Liège charges 8.0%; Charleroi charges 8.5%; Antwerp 7.0%, Ghent 6.5% and the City of Brussels 4.9%, with the national table running from 0% in Knokke-Heist to 9.0% in Mesen. On the same salary that is a meaningful annual difference, and in an agglomeration where Seraing, Herstal, Ans and Chaudfontaine are all separate communes, it is decided by which side of a boundary your lease is on.

Source: FPS Finance — communal tax rates for assessment year 2026

The pre-2022 Belgian expat regime no longer exists, and its replacement was rewritten for 2025.

The special regime for foreign executives was abolished on 1 January 2022 and replaced by the inbound taxpayer regime and the inbound researcher regime. For remuneration from 1 January 2025 the tax-free expense allowance rose from 30% to 35% of gross, the €90,000 annual cap was abolished, and the minimum gross salary condition fell from €75,000 to €70,000, with researchers subject to no salary minimum. Social security did not follow, so the 30% and €90,000 limits still apply for contributions and payroll now diverges from tax. Almost everything written online describes either the abolished regime or the 2022–2024 version.

Source: FPS Finance; professional-firm circulars on the 2025 reform

Liège is a border city, and cross-border employment is a different tax problem from foreign income.

Germany, the Netherlands and Luxembourg are all within about an hour, and a real number of people here work in one country and live in another. That engages double-tax treaties, the EU social security coordination rules on which country's system you contribute to, and — for remote work across a border — the special framework agreement on telework, which not every neighbouring state has joined on the same terms. This is the single most common way a Liège tax return goes wrong, and it is not something to work out from a forum.

Source: FPS Finance

The employer, not you, applies for the inbound regime, and there is no second attempt.

The regime is claimed by the employer within a defined period of the employment starting. Miss that window and it is unavailable for that engagement, permanently — which for a benefit running up to five years and worth as much as 35% of gross as tax-free reimbursement is an expensive oversight. Large employers that hire internationally know the deadline; a Walloon SME or a research institute hiring its first foreign specialist may never have heard of it. Raise it explicitly during negotiation.

Source: FPS Finance

Common mistakes to avoid

Assuming 'Liège' means the City of Liège's 8.0% rate when your address is in a different commune with a different one.
Relying on anything written about the pre-2022 expat regime.
Letting the employer's window to apply for the inbound regime lapse.
Treating cross-border employment in Germany, the Netherlands or Luxembourg as a filing detail rather than a planning question.
Failing to declare foreign bank accounts, foreign life insurance or foreign property.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.