Deductible professional expenses of the self-employed
Professional expenses lower both the social-contribution base and the personal income tax base. The choice between the legal lump sum and actual costs is therefore decisive for the net income of a Belgian sole trader.
1. Legal lump sum
Failing to prove actual costs, the self-employed person gets a lump sum computed as a percentage of gross income, capped at an annual amount. The simplest option, favorable when real charges are low.
2. Actual costs
Actual costs allow deducting all justified professional spending: rent or share of the home, car, depreciation, equipment, (partly) entertainment, professional insurance, accountant.
They require rigorous bookkeeping but are almost always more favorable once charges are significant.
3. Deductible social contributions
The INASTI contributions paid are themselves deductible professional expenses. They reduce the year's taxable income, which this calculator accounts for.
4. VAPZ and insurance
The voluntary supplementary pension premium is deductible within a percentage of net income and an absolute cap. Private hospitalization insurance is generally not deductible for the natural person but remains an expense to budget.
5. Combined effect on net
Each euro of deductible cost avoids both ~20.5% contributions and tax at the marginal rate. The cumulative effect can exceed 60% for high incomes: documenting costs well is one of the main legal optimization levers.