General logic of the payslip
A classic Belgian payslip always follows the same descending structure:
The rest is detail. Once you master these 6 lines, the rest becomes readable.
Gross salary
It's your contractual base salary + variable elements of the month (overtime, premiums, commissions, double holiday pay, year-end premium, etc.).
On the payslip you often see several lines:
- Monthly salary or Hourly rate × hours
- Overtime (usually at 150% or 200% depending on time)
- Premiums (year-end, performance, etc.)
- Holiday pay (paid in May-June for white-collar)
- Guaranteed salary (in case of illness, leave)
Employee ONSS contributions
First deduction on your gross: employee social security.
This 13.07% finances:
- Legal pension (~7.5%)
- Health insurance (~3.55%)
- Unemployment (~0.87%)
- Various solidarity contributions
Your employer also pays on their side approximately 25 to 27% in employer ONSS contributions — which don't appear on your payslip but constitute your total "employer cost".
The work bonus (low and medium salaries)
If you earn a low or medium salary, you benefit from the "work bonus". Concretely, the State refunds part of ONSS contributions to increase your net without raising employer cost.
On the payslip, it often appears as a separate line: "Work bonus" or "Structural reduction". The amount can reach €250/month for low salaries.
Withholding tax (précompte professionnel)
It's the advance on your annual tax (IPP) that your employer withholds each month and remits to FPS Finance. Calculation depends on:
- Your taxable salary for the month
- Your family situation (single, married, legally cohabiting)
- Number of dependent children
- Any declared disabilities
Withholding tax isn't final tax: it's an advance. At annual declaration, you can be reimbursed if too much (or owe more if too little).
From taxable to net
The simplified standard calculation, for a reference salary:
This calculation is indicative. Real net depends on your tax situation, benefits in kind, meal vouchers, etc.
Benefits: read carefully
Meal vouchers
On the payslip, they generally appear as a net benefit (not subject to ONSS or withholding) if legal conditions are met: maximum €8/day, minimum employee contribution €1.09.
Company car
Appears as a "benefit in kind" (ATN/VAA) on the gross line. This benefit is added to your taxable salary, which increases your withholding. Calculation depends on model, CO₂ emissions, and vehicle age.
Group insurance (supplementary pension)
Employer contribution doesn't appear as taxable benefit at contribution time (taxed partially at payout via 16.5% or 10% tax). If you contribute personally, it appears as deduction.
Bicycle allowance
Exempt up to €0.35/km. Appears on a separate line or in "other benefits".
Common mistakes to spot
What to do in case of error
- Document: screenshot or photocopy of concerned payslip
- Compare with your contract, amendments, and your sector's CBA
- Contact your HR service in writing (email) with precise question and expected calculation
- Request correction on next payslip or supplement if already paid
- In case of blockage: FPS Employment or union can intervene
You have 5 years to claim back salary. After that, prescription.
In summary
A Belgian payslip is essentially: gross → ONSS → taxable → withholding → net. The rest are adjustments (benefits, specific deductions, premiums). Once you master this backbone, you can spot anomalies in minutes.
And remember: your real employer cost is about 1.3 × your gross — useful to know on the day you negotiate a raise.