For employees
Working less: how much net pay do you give up?
Want to work 4/5 or half time? Enter your gross salary and your current and new hours. You immediately see how much net pay you give up per month, and for each 4-hour step what you keep. Net pay falls less sharply than gross pay: below you can see why.
Working fewer hours
| Breakdown | Amount |
|---|
Per step: what do you keep?
Your hourly wage stays the same; only your hours change. The row for your new hours is highlighted. Cost per hour off = what you give up in net pay per month, divided by the hours you work less per month ((current − new hours) × 52 ÷ 12).
| Hours per week | Gross per month | Net per month | Net difference compared with now | Net per hour worked | Cost per hour off |
|---|
On a narrow screen we show fewer columns. On a larger screen you also see gross per month and net per hour worked.
Worth noting
Explanation: working less in Belgium, how much net pay do you give up?
Are you working part time, your gross salary falls in proportion to your hours: from 40 to 32 hours (4/5) is 20% less gross. Your net falls less sharply, because withholding tax is progressive. You pay the most on your highest euros, and they are the first to go. The reduction for the tax-free allowance stays the same, so it weighs more heavily at a lower salary.
The work bonus does not simply increase when you work less. For part-time workers, social security (RSZ) calculates it on your salary converted to full time, and you receive that amount in proportion to your hours. With few hours, withholding tax and the special social security contribution disappear. There, each hour less costs you almost your full hourly wage minus 13.07% social security.
If you take time credit, a landing job or thematic leave such as parental leave, the RVA may pay a career break benefit. That is not included in this calculation.
Frequently asked questions
How much net pay do I give up if I go to 4/5?
With €3,500 gross a month for 40 hours, you go to €2,800 gross for 32 hours. Net pay goes from €2,400.40 to €2,064.22 a month: €336.18 less (14%), while you work 20% less. Going to 36 hours costs you €166 net a month. Assumption: single salaried employee without dependent children.
Why does my net pay fall less than my gross pay?
Because withholding tax is progressive. In the example it falls from €617.41 to €352.78 a month, from 17.6% to 12.6% of your gross salary. Social security stays at 13.07% and so simply falls proportionally.
Do I get the work bonus if I start working part time?
Only if your salary converted to full time is low enough: part A stops from €3,403.62 a month. If you work part time, social security (RSZ) calculates the work bonus on that full-time salary and you receive it in proportion to your hours. With €3,500 full time you therefore do not get it, not even if you work less.
Do I have the right to work part time?
Through time credit with a motive (for example to care for your child or follow training), a landing job (half time or 1/5, as a rule from age 55) or thematic leave such as parental leave, you can reduce your hours if you meet the conditions. The conditions and benefits are in the RVA information sheets. Outside those schemes, you agree fewer hours with your employer.
What is the minimum number of hours I must work?
A part-time week must as a rule be at least 1/10 of the full-time week at your employer, and each work period at least 3 hours. A royal decree or collective agreement may deviate from this (FPS Employment).
What happens to my holiday pay and year-end bonus?
They usually fall proportionally. Your holidays and double holiday pay next year depend on what you work this year. This calculator only shows your monthly salary.
Why does an hour less cost almost my whole hourly wage when I work few hours?
Because withholding tax and the special social security contribution disappear at a low salary. With €3,500 for 40 hours, you no longer pay withholding tax from 16 hours: net is then your gross salary minus 13.07% social security. From 16 to 12 hours you give up €304.26 net on €350 gross.
Note: indicative, not advice
This calculation is an indication based on general statutory rules and 2026 rates and does not constitute tax, legal or payroll advice. Assumptions: salaried employee in the private sector, your hourly wage stays the same and your gross salary falls in proportion to your hours. The work bonus for part-time workers follows the social security (RSZ) instructions: calculated on your salary converted to full time, multiplied by your work fraction (rounded to 2 decimals). Withholding tax is approximated with the key formula (single, no reductions other than for dependent children). Not included: career break benefits from the RVA, double holiday pay and year-end bonus, the effect on your pension and social rights, and sectoral agreements. Indicative, not advice. No rights can be derived from this result.
Something wrong or missing? Let us know
Sources & values used
| Item | Amount | Status |
|---|---|---|
| Gross per step | monthly salary × new hours ÷ current hours (hourly wage stays the same) | assumption |
| Employee social security | 13.07% | RSZ/ONSS |
| Work bonus part time | amount at the salary converted to full time × work fraction (max. 1) | RSZ/ONSS |
| Withholding tax | key formula from 1-1-2026 | approximation |
| Cost per hour off | net difference per month ÷ ((current − new hours) × 52 ÷ 12) | calculation rule |
| Minimum part-time week | 1/10 of the full-time week; each work period in principle at least 3 hours | FPS Employment |
| RVA benefit (time credit, thematic leave) | not included | note |
- Social Security (socialsecurity.be) – Which contributions does an employer pay? (incl. 13.07% employee, structural reduction) (in Dutch)
- RSZ/ONSS – Administrative instructions: work bonus (amounts from 1 September 2026) (in Dutch)
- FPS Finance – Calculating withholding tax (key formula from 1 January 2026, Annex III Royal Decree/ITC 92, Belgian Official Gazette 29-12-2025) (in Dutch)
- RSZ/ONSS – Administrative instructions: special social security contribution (in Dutch)
- FPS Employment – Part-time work (minimum weekly working time 1/10, minimum duration per work period 3 hours) (in Dutch)
- RVA – Time credit with a motive, private sector (information sheet T160) (in Dutch)
- RVA – Time credit landing job: right with the employer (half time or 1/5, as a rule from age 55) (in Dutch)
- RVA – Parental leave (thematic leave: full, 1/2, 1/5 or 1/10) (in Dutch)
- FPS Employment – Guaranteed average minimum monthly income (GMMMI) (in Dutch)
Checked on 8 October 2026.