Whether you are taxed on your personal income in Belgium depends on your status. Evidently you will only pay taxes on your personal income to the Belgian State if you are on a Belgian payroll. The amount of taxes you pay will depend on the level of your income and is calculated in percentages per installment.
For residents, this tax applies to all worldwide sources of income, including: salary and employment benefits, interest from savings and investments, rental income. Indeed, regarding the agreement to avoid double taxation existing between Belgium and your country of origin, you will probably be exempt from taxation in Belgium on your foreign (non-Belgian) income. However, your other taxable income earned or received in Belgium will be taxed at the rate as if all of your income (both Belgian and foreign) was taxable in Belgium. (This is the so-called “exonération avec réserve de progressivité” or “vrijstelling met progressievoorbehoud”). Note that non-residents only pay income tax on anything they earn from Belgium.
Furthermore municipal taxes on utilities, including TV, trash collection, and water, are levied by the relevant regions, provinces, and municipalities (communes/gemeenten). You pay these at the same time as income tax, as a surcharge at rates of up to 9% of the tax owed.
If you work as a self-employed person or an employee under the Belgian system, you will pay taxes. As an employee the State will directly deduct a fairly precisely calculated advance for the taxes and social security contributions from your wages. As a self-employed person however you can from your own free pay advances, although this is not mandatory. Employee and self-employed persons will need to fill in their annual tax form, which can be done on line via TaxonWeb and will be partly prefilled by the State.
European civil servants are not required to pay Belgian personal income tax, since they fall under the Protocol on the Privileges and Immunities of the European Communities. As a result the salaries paid by European institutions are exempt from national income tax.
Officials of European institutions who are domiciled for tax purposes in Belgium must complete the tax return but are required to tick special boxes (1062-05/ 1020-47) exempting them from taxes on their salary.
For those who are not domiciled for tax purposes in Belgium, the tax return should be sent to the local tax office (not to the scanning centre) with the relevant letter from the institute.
In the event officials have an income from a Belgian source, this income must be declared in a non-residents tax return, the competent tax office should be notified and this form should be filled out. Once this request has been submitted, you will receive the declaration each year. You must also inform your tax office in the event of a change of address and/or civil status (marriage, legal cohabitation, separation, divorce, death, etc.).
Please note that tax residency varies depending on several factors, domicile, source of income, place of work, family home, and so on. That’s why it is sometimes necessary to consult a tax adviser if you have any doubts about the application of this concept.
Seconded National Experts (SNEs) to international organisations are not employed by them. The tax situation may vary on a case-by-case basis, and they may potentially be subject to personal income tax or non-resident income tax. In most cases the SNE is an official of a Member State and remuneration paid by that Member State is taxable in that Member State. All other allowances paid by the international organisation are however taxable in Belgium.
Official trainees (stagiaires) at the European institutions are not covered by the Protocol on the privileges and immunities of the European Communities so they must complete and return their annual tax form. The training agreement implies the exercise of paid work in a subordinate relationship constituting a contract of employment and, consequently, the indemnities granted within the framework of the SCHUMAN scholarship represent taxable remuneration within the meaning of Articles 30, 1°, and 31, paragraph 2, 1°, of the 1992 Income Tax Code.
However, grants awarded to trainees by the European Union are in principle not subject to income tax in Belgium if the trainee comes in Brussels only for the duration of the traineeship and if the activity in Belgium is carried out for less than 183 days (6 months).