Everything you need to know about starting as self-employed in a secondary occupation in Belgium (2026)

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Starting a secondary occupation is a great way to dip your toes carefully into self-employed life. But how exactly do you become self-employed in a secondary occupation in Belgium? What do you need to know about taxes, VAT, and social contributions? And what are the pros and cons? In this article you will find the answer to all your questions.

Self-employed in a secondary occupation: what is it?

Being self-employed in a secondary occupation is a legal status that describes a person with a primary salaried job who also carries out a self-employed activity alongside it. In Dutch it's called 'zelfstandige in bijberoep', and in French it's 'indépendant à titre complémentaire'.

You probably know someone like this: the teacher who photographs weddings at weekends, or the civil servant who writes freelance copy.

Most people with a secondary occupation choose this status because they want to keep the security of a steady income while gradually building up their client base.

Do you also need to register as self-employed if you only earn a little on the side occasionally? Not straight away. Small, one-off earnings (think: once or twice a year) can be declared in your personal income tax return under “miscellaneous income”. But if you earn regularly or on a professional basis, you are required to register as self-employed (in a secondary occupation).

1. Conditions for starting in a secondary occupation

To be allowed to be self-employed in a secondary occupation, your primary activity must provide you with sufficient social protection. In practice, this means:

• You are an employee working at least half-time
• You are a teacher working at least 6/10 of a full timetable if permanently appointed, or at least 5/10 if not yet permanently appointed
• You are legally retired
• You are seeking employment and the RVA/ONEM has given you permission via the Springboard to Self-Employment programme (which allows you to retain your unemployment benefit for 12 months)
• You receive a benefit from your health insurance fund based on a previous salaried activity

Do you work less than half-time, or are you on unpaid leave? Then you are considered self-employed in a primary occupation, even if you think of it yourself as just earning a bit on the side.

💡Tip: before you start, check whether your employment contract requires permission for secondary activities. Some employers do require this.

2. How do you register as self-employed in a secondary occupation?

To start as self-employed in a secondary occupation, you need a company or VAT number and must arrange a number of administrative formalities.

Starting in a secondary occupation involves four steps:

Step 1: Open a business bank account

Technically this is not mandatory for a sole trader, but we strongly recommend it. It separates your personal and professional finances and makes your bookkeeping considerably cleaner.

Accountable offers a free business account for people self-employed in a secondary occupation, so you keep more of your hard-earned money.

Step 2: Join a social insurance fund

This is mandatory. A social insurance fund collects your social contributions and manages your social rights as a self-employed person. You can choose from Acerta, Liantis, Xerius, Partena, UCM, or another social insurance fund.

Your social insurance fund can also help you with step 3, or make things easy for yourself and use our registration tool to start your secondary occupation (in collaboration with Partena Professional).

Step 3: Request your company registration number via the CBE

To make your secondary occupation official, you must register with the Crossroads Bank for Enterprises (CBE) via an accredited business counter or via Accountable (see step 2). This costs €111.50.

Step 4: Activate your VAT number

After registering with the CBE, you will receive your company registration number, which you then need to have activated as a VAT number (cost: €70).

Your VAT number is your company registration number preceded by "BE". Do not skip this step, even if you opt for the VAT exemption for small businesses. You need your VAT number for the annual client listing.

3. How much does it cost to start in a secondary occupation?

You should budget around €190 to complete your registration, plus €98.51 per quarter in social contributions, but only if you earn more than €1,922.16 per year. If you earn less, you pay no social contributions.

These costs are 100% tax-deductible.

4. How much in social contributions do you pay in a secondary occupation?

Social contributions are mandatory quarterly payments to a social insurance fund, which give you access to social protection such as a pension and health insurance.

As someone self-employed in a secondary occupation, you are required to pay social contributions based on your net taxable income. That is your gross income minus all deductible professional expenses and minus your social contributions, because social contributions are themselves fully deductible as a professional expense, something starters sometimes overlook.

The rules work as follows:

• Income below €1,922.16/year: you do not need to pay social contributions.
• Income between €1,922.16 and €17,374.08/year: you pay a reduced rate — as a starter, that is €98.51 per quarter.
• Income above €17,374.08/year: you pay the same rate as a self-employed person in a primary occupation: 20.5% on your net taxable income up to €75,024.54, and 14.16% on the portion above that up to €110,562.42.

After three years, your provisional contributions are recalculated based on your actual income. Earned more than expected? You pay the difference. Earned less? You receive a refund of the excess paid.

One silver lining: your social contributions are 100% tax-deductible.

💡Read more about social contributions for people self-employed in a secondary occupation.

5. What social rights do you build up through your secondary occupation?

As long as you pay no or reduced contributions as someone in a secondary occupation, you do not build up any additional social security rights through your self-employed status.

You retain the rights you build up through your primary occupation as an employee or civil servant, including pension, health insurance, and incapacity for work cover.

If you do pay contributions at the primary occupation rate (income above €17,374.08), you build up in principle the same rights as a self-employed person in a primary occupation.

6. Secondary occupation and taxes

Income from your secondary occupation is taxed as professional income in personal income tax, on top of your salary as an employee. This means it is taxed according to the progressive tax brackets, which can quickly amount to 40% or even 50%.

An example:
Your gross annual salary as an employee is €46,000. Your secondary occupation yields €5,000 (after deducting expenses). That €5,000 is added to your salary, pushing you into the highest tax bracket of 50%.

The golden tip: claim sufficient professional expenses. Costs you incur for your self-employed activity are deductible from your taxable income: laptop, mobile phone, internet subscription, workspace, travel, professional software… But this does not necessarily mean you need to spend extra money to claim expenses. As someone in a secondary occupation, you can also claim a portion of your existing internet, water, and electricity bills.

The more legitimate expenses you deduct, the lower your taxable income. If you have few expenses, opt for the standard flat-rate deduction.

7. Are you liable for VAT in a secondary occupation?

Even as someone self-employed in a secondary occupation, you are in principle required to charge VAT on your products or services. However, if your annual turnover is below €25,000, you qualify for the VAT exemption scheme for small businesses.

In that case, you do not charge VAT to your clients and do not submit VAT returns — but equally, you cannot reclaim VAT on your purchases.

Do you exceed €25,000? Then you become VAT-liable and submit quarterly returns. Accountable handles this automatically based on the invoices you enter.

8. How much can you earn as someone self-employed in a secondary occupation?

There is no income cap. You can earn as much as you like in a secondary occupation.

Higher income naturally leads to higher social contributions and a higher tax burden, but there is no threshold at which you are required to switch to a primary occupation status, as long as your primary activity as an employee or civil servant remains intact.

9. The pros and cons of a secondary occupation

Starting a secondary occupation has advantages and disadvantages. You can pursue your passion and earn extra income, but you may also pay a considerable amount of tax on it.

Advantages:

• You retain the security of a steady salary and social protection through your primary occupation
• If your income is low, you pay no social contributions
• You test your business idea without risking everything
• Professional expenses are tax-deductible
• Until 2027, you can deduct 120% of the costs for e-invoicing software from your taxable profit

Disadvantages (and how to solve them):

• Heavy tax burden: your secondary income is added to your primary occupation income, potentially pushing you into a higher tax bracket. → Claim maximum professional expenses and make advance tax payments on time via Accountable.
• Administrative obligations: VAT returns, client listing, tax return… → Accountable largely automates this.
• Limited time: alongside a full-time job, available time is scarce. → Choose an activity you can build up at your own pace.
• Limited social rights: as long as you pay reduced contributions, you do not build up extra pension rights. → Consider a VAPZ (free supplementary pension for the self-employed) if your income exceeds €17,374.08.

Is it a good idea to start as self-employed in a secondary occupation? That is ultimately for you to decide. To help you, we have listed all the pros and cons in a separate article.

10. When do you become self-employed in a primary occupation?

You are required to switch to the status of self-employed in a primary occupation if you no longer meet the conditions for a secondary occupation. For example, if your primary activity as an employee or civil servant falls away or drops below the half-time threshold.

You can also switch voluntarily, which may be worth considering if your secondary income approaches your primary salary. Different rules apply upon switching: there is a minimum contribution of €917.58 per quarter (2026), but also more social rights.

Accountable is here for you

Becoming self-employed is a real adventure. But you do not have to take on the admin along with it. Accountable manages your bookkeeping, VAT returns, and tax return, designed specifically for Belgian self-employed people in both secondary and primary occupations.

Try Accountable now for free ✨

Author - Nicolas Quarré

Nicolas is co-founder and CEO at Accountable. His vision for the company has always been clear: free self-employed from administrative nightmares.

Who is Nicolas ?