Summary
Belgium has one of the highest tax burdens in Europe. Employers withhold income tax (bedrijfsvoorheffing / precompte professionnel) and social security contributions (RSZ / ONSS) from each payslip. Income tax is progressive with four brackets, but a generous personal allowance of €10,910 means the first slice of income is tax-free. On top of the federal income tax, municipalities levy a surtax (typically around 7%) on the tax due.
How it works
Your take-home pay is your gross salary minus three deductions:
- RSZ/ONSS social security - 13.07% of gross salary, deducted first (uncapped)
- Federal income tax - progressive rates on income above the personal allowance, applied to gross minus social security
- Municipal surtax - a percentage (typically ~7%) applied to the federal income tax amount
Social security is deducted before tax, so the taxable base for income tax is your gross salary minus the 13.07% RSZ contribution.
Income Tax Bands (2025)
Belgium’s federal income tax uses four brackets, applied to taxable income above the personal allowance:
| Taxable income (above allowance) | Marginal rate |
|---|---|
| Up to €15,820 | 25% |
| €15,821 - €27,920 | 40% |
| €27,921 - €48,320 | 45% |
| Above €48,320 | 50% |
Personal Allowance
The tax-free personal allowance for 2025 (income year) is €10,910. This amount is exempt from income tax. The allowance increases with dependants (children, disabled spouse, etc.).
These are marginal rates - each rate applies only to the income within that band.
Social Security Contributions
Belgian social security (RSZ / ONSS) is a single flat rate for employees:
| Component | Employee rate |
|---|---|
| RSZ / ONSS (total employee contribution) | 13.07% |
The employee rate of 13.07% applies to the entire gross salary with no cap. This is one of the highest employee social security rates in Europe. The contribution covers pensions, healthcare, unemployment, and other social benefits.
Employers pay an additional ~25% on top of gross salary (not deducted from the employee).
Municipal Surtax
Municipalities levy an additional surtax on federal income tax. The rate varies by municipality but averages around 7% across Belgium. This is applied to the federal tax amount (not to income), so:
Municipal tax = Federal income tax x municipal surtax rate
The formula
Where
Worked example
EUR 45,000 gross annual salary (7% municipal surtax)
RSZ social security (13.07% of gross)
= EUR 5,881.50
Taxable income for federal tax
= EUR 39,118.50
Income above personal allowance (EUR 10,910)
= EUR 28,208.50
First EUR 15,820 at 25%
= EUR 3,955
Next EUR 12,100 (EUR 15,821 - EUR 27,920) at 40%
= EUR 4,840
Remaining EUR 288.50 (EUR 27,921 - EUR 28,208.50) at 45%
= EUR 129.83
Federal income tax
= EUR 8,924.83
Municipal surtax (7% of federal tax)
= EUR 624.74
Total deductions
= EUR 15,431.07
Result
Take-home pay = EUR 45,000 - EUR 15,431.07 = EUR 29,568.93/year (EUR 2,464.08/month)
Assumptions & limitations
- Uses the 2025 federal income tax brackets and personal allowance of €10,910
- The municipal surtax of 7% is an estimate - actual rates range from 0% to 9%+ depending on the municipality (Brussels communes average ~6-7%, Flemish municipalities vary widely)
- Does not model the employment expense deduction (forfaitaire beroepskosten) which reduces taxable income by a percentage of employment income (capped at ~€5,750)
- Does not model special social security contribution (bijzondere bijdrage sociale zekerheid), an additional income-dependent levy of approximately €0-€731/year
- Assumes a single taxpayer with no dependants (the personal allowance increases with children and other dependants)
- RSZ is uncapped - unlike most EU countries, there is no ceiling on employee social security contributions
- Belgium pays in 13.92 months (holiday pay + 13th month) - the annual total is the same regardless
- Does not model: meal vouchers, eco vouchers, company car benefit, group insurance, or other common Belgian salary components