Flexi-jobs
A flexi-job lets you work alongside your main job, or after retirement, under a tax-friendly arrangement. Belgium taxes this income differently from a regular salary, which is exactly what makes it worth understanding before you take one on.
This page explains who a flexi-job is generally for, how the tax exemption works, and what happens if your flexi-job income goes over the yearly limit.
Overview
A flexi-job is extra work you take on alongside a main job, or as a pensioner, taxed under a more favourable regime than ordinary employment income. In exchange for a special 28% social contribution paid on your flexi-job earnings, the income itself can be fully or partly exempt from income tax - but only if you meet the eligibility conditions and stay within the applicable limits.
Who a flexi-job is for
Whether you're eligible for a flexi-job depends mainly on your main employment situation, or your status as a pensioner. The exact social-law conditions - things like how much you need to already be working in your main job - are set by the National Social Security Office (RSZ/ONSS), not by the tax rules covered on this page. If you're checking whether you personally qualify, RSZ's website is the right place to confirm the current conditions before assuming either way
How the tax exemption works
How your flexi-job income is taxed depends on whether you're a pensioner or not.
If you're a pensioner: your flexi-job income is fully exempt from tax, regardless of the amount. You're considered a pensioner if you receive a statutory first-pillar pension, including early retirement or a survivor's pension - transitional allowances don't count. Your status is assessed at the moment you actually do the work, not when you're paid, so if you're unsure which category you fall into, RSZ can confirm this too.
If you're not a pensioner: your flexi-job income is exempt up to an annual ceiling, which is indexed each year:
Income earned in 2025 (tax year 2026): €18,000
Income earned in 2026 (tax year 2027): €18,440
Allowances not subject to the special contribution, such as commuting reimbursements, don't count towards this ceiling. If you're only taxable in Belgium for part of the year - for example, if you arrive or leave partway through - the ceiling is reduced proportionally to match the number of months you're taxable here.
If you go over the limit
The ceiling applies to all your flexi-job income combined, even if you work for more than one employer. If your total goes over the limit, only the amount above the ceiling becomes taxable, at the same rate as ordinary salary - the rest stays exempt.
If this happens with a single employer, they report the taxable portion and withhold tax on it directly. If you work multiple flexi-jobs and each employer individually pays you below the ceiling, but your combined income across all of them goes over it, you don't need to calculate this yourself - it's worked out automatically when your tax return is processed, based on the income slips (fiche 281.10) from each employer.
Good to know: the exemption ceiling is indexed annually, so the number that applies to you depends on the specific year you're asking about - always check the current figure on the official FOD Financiën page rather than relying on last year's amount. If you're not sure whether your main job or pensioner status actually qualifies you for a flexi-job in the first place, that's a separate question for RSZ, not something the tax rules alone can answer.
Sources
- FOD Financiën - Flexi-jobs
- RSZ / ONSS
