Self-employed as a secondary occupation in 2026: how much will I really keep?

Who is self-employed as a secondary occupation?

You are if your main activity occupies you at least half-time:

• Employee: a job of at least half-time. Unpaid leave makes you self-employed as a main occupation again.
• Tenured teacher: at least 6/10 of a full timetable; from 5/10 to 6/10, assimilation under Article 37 can be requested. A contract teacher: half-time is enough.
• Civil servant: at least 8 months or 200 days a year, half-time each month.
• Unemployment, incapacity for work: only if your benefit reaches at least the minimum pension of a single self-employed person. Otherwise, you are self-employed as a main occupation. When unemployed, the activity must also be declared to the National Employment Office (NEO) before you start: what you can combine.

If your job ends, notify your social insurance fund within 15 days: you become self-employed as a main occupation, with a minimum contribution of €890.42 a quarter.

Survivor’s pension, married spouse of a person with their own rights, political office holder: this is Article 37, a similar scheme, with 20.5% between €1,922.16 and €9,101.26 and at most €466.44 a quarter. Student: a separate status, with no contribution below €8,687.04.

Social security contributions

They are calculated on the activity’s net taxable income: receipts minus expenses, minus the contributions themselves, which are deductible. No steps: the formula is continuous.

With zero or reduced contributions, you do not build up additional social rights: your protection comes from your job. From €17,374.08 of income, you in principle build up the same rights of your own as a person self-employed as a main occupation.

The pitfall at the start: the adjustment

During your first three full calendar years, your fund does not yet know your income: it charges a provisional contribution of €98.51 a quarter (excluding management fees). When the tax authorities send it your actual income, it makes an adjustment: usually within two years, sometimes up to the third year for a starter. No official deadline is published.

Example: with €10,000 of consulting receipts in the first year, with no actual expenses, you pay €394.04 in provisional contributions (plus fund fees). Your net taxable income is then about €7,189, and the final contribution €1,473.81. The additional amount of about €1,080, plus fund fees, will come later: set it aside now. It will be deductible in the year you pay it.

You can ask for a lower provisional contribution by showing that your income will stay low. But if your actual income exceeds the reduced base, you pay the additional amount and surcharges.

Actual expenses or flat-rate expenses

If you do not declare actual expenses, the tax authorities apply flat-rate expenses, separate from those of your salary. You cannot mix flat-rate and actual expenses for the same activity.

For €10,000 of receipts with no actual expenses, the flat-rate expenses reach €2,309.02 for professional income and €2,612.05 for business profits. If your actual expenses are higher, deduct them: keep the invoices.

These flat-rate expenses reduce the net taxable income, and so also, in principle, the base for social security contributions: what counts is the income ‘set by the tax authorities’. No source we read says so in so many words: confirm it with your fund.

Tax

The activity’s income is added to your salary and taxed with it, at the rate of the band it falls into, plus the municipal tax. With €3,000 gross a month and €10,000 of receipts, the extra tax amounts to about 45.7% of the activity’s net taxable income, and each additional euro is taxed at about 48.2%.

With a small salary, part of it can remain tax-free: at €1,200 gross half-time, the first €1,642 of net taxable income give rise to no extra tax. This amount depends on the tax-free amount for 2026 income: Indexo applies €11,550, the amount in the reform that was voted, but some sources still cite €11,180. With that amount, the tax-free part would be smaller: check before counting on it.

Advance tax payments (voorafbetalingen / versements anticipés): from 2026 income, not making them no longer leads to a tax increase for self-employed individuals trading in their own name (Act of 15 July 2026, according to Securex: we have not read the Belgian Official Gazette). They still earn a bonus:

Without advance payments, the tax on the activity arrives with the tax assessment notice (aanslagbiljet / avertissement-extrait de rôle) the following year: how much to set aside.

VAT and e-invoicing

• Small business VAT exemption scheme: below €25,000 of receipts a year (pro rata if you start during the year), you can invoice without VAT, with the statement ‘Régime particulier de franchise des petites entreprises’. You remain VAT-registered, with a VAT number, but without periodic returns.
• Exceeding by less than 10%: the sources contradict each other. According to the FPS Finance sheet quoted by Forum for the Future and Securex, the exemption remains valid until the end of the year; according to the OECCBB and Deg & Partners, it ends immediately. Check with your accountant before acting.
• Future thresholds: a bill adopted by the Chamber on 17 September 2026 provides for €26,000 in 2027, €27,000 in 2028, €28,000 in 2029, €29,000 in 2030, €30,000 in 2031. Its publication has not been confirmed.
• Peppol: since 1 January 2026, your invoices to Belgian businesses go through the Peppol network, including under the exemption scheme. For private clients, you only need to be able to receive Peppol invoices. Fines provided for: €1,500, then €3,000, then €5,000.

Up to how much without paying?

Each scheme has its own threshold, and it is not the same for contributions, tax and VAT:

Above the €7,890 ceiling, all sharing economy and associative work income for the year becomes professional income, not just the excess.

Self-employed as a secondary occupation or Smart?

Through Smart, your client pays the cooperative, which pays you a salary: you remain an employee, with no enterprise number or social insurance fund. But Smart withholds a 6.5% contribution, then the budget covers the employer contributions (employment budget = gross salary × 1.55) and your own.

For the same receipts, the person self-employed as a secondary occupation keeps significantly more. Smart makes sense mainly for a few one-off assignments, for an artist, or if you value an employee’s social rights. See also invoicing without being self-employed.

Getting started: the checklist

1. Check that your employment contract does not prohibit the activity (exclusivity clause, non-compete) and, if unemployed, apply to NEO.
2. Join a social insurance fund before the first day of activity.
3. Register with the Crossroads Bank for Enterprises through a enterprise counter: €111.50 in 2026.
4. Activate VAT, or apply for the small business VAT exemption scheme (form 604B).
5. Choose Peppol invoicing software if you have business clients.
6. Open a bank account for the activity and keep all expense invoices.
7. Set aside the contributions for the adjustment and the following year’s tax.

Frequently asked questions

What next?

• Create an invoiceCompliant invoices, as a PDF and a Peppol file, free.
• Invoicing without being self-employed?Smart, social offices for artists, cooperatives, Paddle and the others.
• Social contributionsMain occupation, secondary occupation, Article 37 and student.
• How much to set aside?The share of each euro received to keep for contributions and tax.
• Earn moreOvertime, flexi-job or side activity: the net pay of each option.