Who counts as self-employed as a side activity?
Someone whose self-employment comes on top of another professional activity. As an employee, your working hours must be at least half of those of a full-time employee in the same company or sector, as INASTI specifies.
Other cases are assimilated: a contract teacher with at least a half schedule, an appointed teacher with at least six tenths, or someone receiving a replacement income from past salaried work, such as an unemployment or incapacity benefit, at least equal to the minimum pension of a single self-employed person. Below these conditions, you are self-employed as a main activity, even if you see it as a side project.
How much do you pay in social contributions?
It depends on your net taxable self-employed income for the year. The thresholds published by INASTI for 2026 are:
- Less than €1,922.16: no social contributions
- From €1,922.16 to less than €17,374.08: a reduced contribution, proportional to your income
- €17,374.08 or more: the same contributions as a main-activity self-employed person
These amounts are indexed, so check them every January. As in a main activity, you first pay provisional contributions and they are adjusted once the tax authorities know your real income. The mechanism is explained in what social contributions a freelancer pays.
How do you start a side activity?
The same way as a main activity: register through a business counter, activate your VAT number if needed, and join a social insurance fund before you start. The steps are listed in how to become self-employed in Belgium.
Much of your social security cover, such as health care, already comes from your job, which is why the contributions are lighter. For VAT, a side activity with a small turnover often fits the franchise regime: no VAT charged and none deducted, up to €25,000 a year excluding VAT, according to the SPF Finance. For IT services sold to companies that recover VAT, the normal regime can be more practical, so compare both before choosing.
Does your employer have a say?
Check your employment contract before you start. Look for an exclusivity clause, a confidentiality clause or a rule on intellectual property, and never work for a direct competitor or a client of your employer without clearing it first: loyalty obligations continue while you are employed.
A side activity is also a way to test freelancing before switching. If you later move to full-time freelancing, your contributions switch to the main-activity rules. The comparison between both statuses is in freelancer or employee: which pays more, and our definition of self-employed status covers the basics.
