Since 1 November 2026, withholding tax on pay has been calculated differently (Royal Decree of 27 September 2026). The calculations on this page still follow the previous rules: for pay received from 1 November, withholding tax and net pay may differ. Update in progress.
Yes, with the authorisation of the medical adviser of your health insurance fund (mutualité / ziekenfonds): this is authorised work, or gradual return to work. As an employee or unemployed person, your benefit is not reduced up to one-fifth of full time; above that, it falls according to the extra hours: at half-time, by 30%. As a self-employed person, it is not reduced for 6 months, then by 10%.
Declare your return no later than the working day before, using your health insurance fund’s single form: you can start without waiting for the written reply. The medical adviser has 30 working days to decide. National Institute for Health and Disability Insurance (NIHDI) rules checked on 7 and 8 October 2026. For guidance only, not medical or legal advice.
One-fifth reductionof authorised work with no benefit reduction, as an employee or unemployed person
30%benefit reduction for a half-time return (19 hours out of 38)
2 yearsat most per authorisation, renewable
6 monthswith no reduction for a self-employed person, then 10% until the end of the third following year
Activity by activity
Any return to work, as an employee or self-employed, requires the medical adviser’s prior approval: the work must be compatible with your state of health, and your capacity for work must remain reduced by at least 50%. Volunteering does not require authorisation, but you must inform the health insurance fund.
Combining an activity with sickness benefits in 2026. Click an activity for the rule for employees and unemployed people; the rule for the self-employed follows further down.
How much of your benefit is left?
Since 2018, for new authorisations, the calculation is simple: the share of your working time above one-fifth of full time is deducted from the benefit, as a percentage. Your pay from the work you take up is added in full. For an authorisation dating from before 1 April 2018, the old calculation still applies if it is more favourable to you.
Swipe the table →
Working time
Benefit reduction
Benefit per month
20%
0%
€1,500.00
30%
10%
€1,350.00
40%
20%
€1,200.00
50%
30%
€1,050.00
60%
40%
€900.00
80%
60%
€600.00
Employee or unemployed person in authorised work, by working time taken up (NIHDI rule). Benefit of €1,500 a month used as an example.
Your case: returning to work during incapacity
The tool is set to a half-time return as an employee. Enter your benefit, the salary and the working time: Indexo calculates the reduction and your total net pay. The amounts shown are an example. Nothing is sent.
The tool could not be displayed. Reload the page (Cmd + Shift + R on a Mac, Ctrl + F5 on a PC).
Employee or unemployed person unfit for work: the detailed rules
A job as an employee
Allowed, subject to conditions
Authorisation from your health insurance fund’s medical adviser: work compatible with your state of health, and capacity still reduced by at least 50%.
This is gradual return to work (adapted work), with your employer or elsewhere; the authorisation sets the nature, volume and conditions of the work.
You can return to work without waiting for the written reply, once the request has been sent.
Ceilings and limits
Authorised work with no benefit reduction up to one-fifth of full time: 20% of full time
Maximum duration of an authorisation, renewable: 2 years (per authorisation, renewable)
Steps
Your health insurance fund (medical adviser): no later than the working day before you return. Single form for the declaration and the authorisation request, supplied by the fund, sent by bpost or handed in against a receipt. inami.fgov.be
Effect
Up to one-fifth of full time, the benefit is not reduced. Above that, it falls according to the hours over that fifth: at half-time (19 hours out of 38), it is reduced by 30%.
Any return to work during incapacity requires the medical adviser’s prior authorisation.
For a self-employed activity by an employee who is unfit for work, the NIHDI does not detail how the reduction is calculated: your health insurance fund will tell you.
Ceilings and limits
Capacity reduced by at least 50% for authorised work: 50% reduction in capacity
Steps
Your health insurance fund (medical adviser): no later than the working day before you return. Single form for the declaration and the authorisation request, supplied by the fund, sent by bpost or handed in against a receipt. inami.fgov.be
Effect
Effect on the benefit calculated by the health insurance fund; to be checked before you start.
A flexi-job is employed work: it requires the medical adviser’s prior authorisation, like any return to work.
Having worked at least four-fifths for another employer in the third quarter before (T-3), or being retired.
Ceilings and limits
Authorised work with no benefit reduction up to one-fifth of full time: 20% of full time
Tax-free flexi-income for non-pensioners, 2026 income: €18,440 a year
Steps
Your health insurance fund (medical adviser): no later than the working day before you return. Single form for the declaration and the authorisation request, supplied by the fund, sent by bpost or handed in against a receipt. inami.fgov.be
Effect
Same rules as for adapted work: no reduction up to one-fifth of full time, then a reduction according to the hours above that.
Associative work is done under an employment contract: it requires the medical adviser’s prior authorisation.
Activities in sport, socio-cultural activities, events or amateur arts, within an association.
No employment relationship with the same organisation in the previous year.
At most 450 hours a year in sport, 300 in other activities.
Ceilings and limits
Sharing economy and associative work together: miscellaneous income ceiling, 2026 income: €7,890 a year
Associative work in sport: 450 hours a year
Associative work in other activities (socio-cultural, events, amateur arts): 300 hours a year
Steps
Your health insurance fund (medical adviser): no later than the working day before you return. Single form for the declaration and the authorisation request, supplied by the fund, sent by bpost or handed in against a receipt. inami.fgov.be
Effect
The NIHDI does not detail the effect of an associative work contract on the benefit: ask your health insurance fund.
Indexo has not found a published rule for this case. Contact: your health insurance fund: for work that is neither employed nor self-employed, the NIHDI refers you to it.
An artistic activity
To be checked with the relevant body
Indexo has not found a published rule for this case. Contact: your health insurance fund: the amateur arts allowance is not covered by the NIHDI in the pages consulted.
Volunteering
Allowed, subject to conditions
Unpaid activity, without obligation, for a non-profit organisation, outside the family setting.
Compatible with your state of health: the medical adviser confirms this.
No prior authorisation, unlike work; inform your health insurance fund as soon as possible.
Ceilings and limits
Tax-free flat-rate allowance, 2026 income: €44.02 a day
Tax-free flat-rate allowance per year, 2026 income: €1,760.83 a year
Steps
Your health insurance fund (medical adviser): as soon as possible, ideally before you start. Request to the medical adviser (annex to circular O.A. 2019/133). inami.fgov.be
Effect
No benefit reduction if volunteer allowances stay within the permitted ceiling.
Indexo has not found a published rule for this case. Contact: your health insurance fund: the NIHDI refers you to it for roles such as lay judge or lay counsellor in the labour courts.
Self-employed and unfit for work
The medical adviser can authorise a return from the 2nd day of recognised incapacity, to your own activity or another one. The authorisation is valid for 6 months, extendable to 18 months if the aim is a full return; otherwise, it can be unlimited. From the 4th year, your income is compared with a ceiling of €23,542.41 (2026): nothing below it, a reduction by the percentage by which you exceed it below 15%, suspension above that.
A job as an employee
Allowed, subject to conditions
The medical adviser can authorise employed work, part-time or with a view to a full return.
Same step as for a self-employed activity, before you start.
Ceilings and limits
Authorised work with no reduction until the end of the 6th month: 6 months
Reduction from the 7th month to the end of the 3rd year after the starting year: 10% of the benefit (thereafter)
Steps
Your health insurance fund (medical adviser): no later than the working day before you return. Single form for the declaration and the authorisation request, supplied by the fund, sent by bpost or handed in against a receipt. inami.fgov.be
Effect
Same reduction rules as for an authorised self-employed activity.
Authorisation from the medical adviser, possible from the 2nd day of recognised incapacity; the work must not harm your health.
Partial return to your activity, or to another self-employed activity.
Duration: 6 months, extendable to 18 months if the aim is a full return; otherwise unlimited, unless the medical adviser decides otherwise.
Ceilings and limits
Authorised work with no reduction until the end of the 6th month: 6 months
Reduction from the 7th month to the end of the 3rd year after the starting year: 10% of the benefit (from the 7th month to the end of the third following year)
Income ceiling from the 4th year of authorised work (2026): €23,542.41 a year
Steps
Your health insurance fund (medical adviser): no later than the working day before you return. Single form for the declaration and the authorisation request, supplied by the fund, sent by bpost or handed in against a receipt. inami.fgov.be
Effect
No reduction until the end of the 6th month; then 10% until the end of the 3rd year after the starting year. After that, your income is compared with the ceiling: nothing below it, a reduction by the percentage by which you exceed it below 15%, suspension at 15% or more.
You must have worked at least four-fifths for another employer in the third quarter before (T-3), or be retired. A self-employed person does not meet this condition, unless they also have a four-fifths job as an employee.
Mandate as a municipal councillor or member of a CPAS/OCMW council (except chair): combination with no reduction.
Other mandates: to be checked with your health insurance fund.
Steps
Your health insurance fund (medical adviser): before you take up the mandate. Single form for the declaration and the authorisation request, supplied by the fund, sent by bpost or handed in against a receipt. inami.fgov.be
Effect
No reduction for a mandate as a municipal councillor or member of a CPAS/OCMW council.
2026 amounts. The 2027 amounts (limits for pensioners, ceilings for the sharing economy and flexi-jobs, thresholds for the self-employed) have not been published yet: they usually are at the end of the year. The pages will switch to 2027 as soon as they are published.
Frequently asked questions
Do you have to wait for the medical adviser’s approval before returning?
No. Send the declaration and authorisation request no later than the working day before you return, using your health insurance fund’s form (by bpost or handed in against a receipt): you can start without waiting for the written reply. The medical adviser has 30 working days to decide.
How much do you lose by returning half-time?
As an employee or unemployed person, the benefit is reduced by the share of working time above one-fifth of full time: at half-time (19 hours out of 38), 30%. Up to one-fifth time, there is no reduction. Your salary is added to the reduced benefit.
Can you volunteer while you are ill?
Yes, without prior authorisation, unlike work. Inform your health insurance fund as soon as possible and ask the medical adviser to confirm that the activity is compatible with your state of health. Expenses can be paid within the permitted ceiling.
Can a self-employed person who is ill keep working?
Yes, with the medical adviser’s authorisation, from the 2nd day of recognised incapacity. The benefit is not reduced until the end of the 6th month, then by 10% until the end of the 3rd year after the starting year.