Why do I have to pay Belgian tax for income year 2025 if I had only one Belgian employer?

For income year 2025, assessment year 2026, having around €300 of Belgian personal income tax still to pay can be normal even with only one Belgian employer. The most common explanation is that the professional withholding tax deducted during the year was slightly lower than the final tax calculated on the annual income. The answer always depends on the taxpayer’s exact figures and situation.

The figures below are illustrative and based on income year 2025, assessment year 2026.

Professional withholding tax is not the final Belgian tax

In Belgium, the professional withholding tax deducted from salary each month is not the final personal income tax.

It is an advance payment. The final calculation is made later through the Belgian tax return and tax assessment notice.

That final calculation takes into account, among other things:

• annual taxable professional income;

• progressive Belgian tax brackets;

• the basic tax-free allowance;

• automatic or actual professional expenses;

• tax reductions and tax credits;

• municipal surcharge;

• professional withholding tax already deducted during the year.

This means that an employee can have only one Belgian employer and still receive a final tax assessment showing a balance to pay.

A typical 2025 example: around €38,000 of taxable remuneration

In a typical case, a fiche 281.10 for income year 2025 may show approximately:

• code 250: taxable remuneration of about €38,100;

• code 286: professional withholding tax of about €7,550;

• employee supplementary pension contributions of around €360;

• a work bonus amount of around €730;

• a small taxable benefit in kind of about €200.

A simplified reconstruction can then lead to a result close to this:

The final result can vary because of rounding, the special social security contribution and the exact calculation made by the tax administration.

But in this type of situation, a balance of around €300 is not necessarily a sign of an error.

The 2025 Belgian tax brackets and professional expenses matter

For income year 2025, the Belgian federal tax brackets used in the analysis were:

• 25% up to €16,320;

• 40% from €16,320 to €28,800;

• 45% from €28,800 to €49,840;

• 50% above that.

The basic tax-free allowance for income year 2025 is €10,910.

Employees also automatically receive flat-rate professional expenses equal to 30% of the relevant professional income, capped at €5,930 for income year 2025.

Once salary reaches a certain level, the maximum flat-rate expense cap is already reached. That means an increase in taxable remuneration can push more income into higher tax brackets without a proportional increase in deductible professional expenses.

Why a small balance can appear even with one employer

A balance due can arise because payroll withholding is only an estimate.

Several factors can make the final annual tax slightly higher than the tax withheld during the year:

• taxable remuneration increased compared with the previous year;

• more income falls into the 45% tax bracket;

• the employee has few personal tax reductions;

• there are no dependants or limited family-related tax advantages;

• year-end premium, holiday pay or variable remuneration changed the annual profile;

• the municipal surcharge applies on top of the federal tax.

On taxable remuneration of around €38,000, a balance of around €300 represents less than 1% of the taxable remuneration. It can be frustrating, but it is not unusual.

Is the balance caused by foreign income?

Not necessarily.

If the fiche 281.10 does not show foreign remuneration, foreign stock options, flexi-job income or income from another employer, the balance is not automatically linked to foreign income.

In this type of case, the more likely explanation is simply that the employer withheld slightly too little professional withholding tax during the year compared with the final Belgian tax calculation.

Meal vouchers, benefits in kind and reimbursements

Meal vouchers are generally exempt from social security contributions and income tax if the legal conditions are met.

Employer cost reimbursements are also not necessarily taxable if they are genuine reimbursements of employer expenses and are not included in ordinary taxable salary.

However, supporting documents remain important. If the tax administration questions whether reimbursements are genuine employer cost reimbursements, the taxpayer may need to justify them.

A small benefit in kind included in taxable remuneration is taxable. But if the benefit is only around €200, it will not usually explain a full tax balance of around €300 by itself.

A non-recurring result-linked benefit shown separately on the fiche should also not be manually added a second time if it has already been treated correctly.

Which tax return codes should be checked?

Before accepting a pre-filled tax return or simplified proposal, the taxpayer should verify that the fiche data has been correctly transferred.

For income year 2025, assessment year 2026, the following points are especially important:

• code 1250/2250 should correspond to the taxable remuneration shown on the fiche 281.10 under code 250;

• code 1286/2286 should correspond to the professional withholding tax shown under code 286;

• code 1285/2285 should correspond to employee supplementary pension contributions;

• the work bonus information should be correctly pre-filled;

• public transport reimbursement should be correctly treated if applicable.

For public transport between home and work, the reimbursement is declared under code 1254/2254 and the exemption under code 1255/2255, provided the relevant conditions are met.

The taxpayer should also check whether any tax-reducing expenses are missing, such as qualifying donations, private pension savings, legal protection insurance, childcare costs or other tax benefits.

Should actual professional expenses be claimed instead of the flat-rate expenses?

Not automatically.

For many employees, the automatic flat-rate professional expenses are more advantageous, especially where commuting or homeworking costs are already partly reimbursed by the employer.

For income year 2025, the employee flat-rate professional expense cap is €5,930.

Actual professional expenses should generally only be considered if the taxpayer can prove that their real deductible expenses exceed the automatic forfait.

What if the taxpayer arrived in Belgium during a previous year?

A separate issue can arise where a taxpayer became subject to Belgian personal income tax during the year, for example in income year 2023.

Belgian tax returns contain a specific field for people who were subject to Belgian personal income tax for less than 12 months during the income year.

The official Brussels explanatory notes state that:

• if Belgian tax liability starts before the 16th day of a month, that month can be counted;

• if it starts on the 16th day or later, that month is normally not counted.

This can affect the tax-free allowance and certain tax advantages because they may be prorated.

If an assessment notice for a partial-year Belgian residence year seems incorrect, the key point is to verify whether the number of months of Belgian personal income tax liability was correctly completed and whether the professional withholding tax was correctly credited.

Deadlines and correction options

For a normal online Belgian tax return via MyMinfin/Tax-on-web for assessment year 2026, the deadline mentioned in the analysis is 15 July 2026.

For a paper return, the deadline is 30 June 2026.

If the tax assessment notice has already been issued and appears incorrect, a motivated objection can be filed within one year from the date the assessment notice was sent.

In some cases, a request for ex officio relief may be possible within five years.

Practical solution for future years

If the issue is simply that payroll withholding is slightly too low each year, the practical solution may be to ask HR or payroll whether they can deduct a small additional amount of professional withholding tax each month.

For example, an additional €25 to €30 per month could broadly neutralise a recurring balance of around €300 to €360 per year.

This does not reduce the total annual tax. It only reduces the risk of having to pay a balance when the final assessment is issued.

Frequently asked questions

Why do I owe Belgian tax if I had only one employer?

Because the professional withholding tax deducted by the employer is only an advance payment. If the final Belgian tax calculation is slightly higher than the withholding tax already deducted, a balance remains payable.

Does a €300 balance mean my Belgian tax return is wrong?

Not necessarily. For income year 2025, a balance of around €300 can be coherent where taxable remuneration is around €38,000 and the withholding tax deducted during the year was slightly insufficient.

Is the balance caused by foreign income?

Only if foreign income is actually present and relevant in the tax return. If the fiche does not show foreign remuneration, foreign stock options or income from another employer, the balance may simply result from Belgian salary taxation.

Should I add a non-recurring result-linked benefit manually?

No, not if it is already shown separately on the fiche and has been correctly treated. Manually adding it again could lead to double taxation.

Can meal vouchers create a Belgian tax balance?

Meal vouchers are generally exempt if the legal conditions are met. They are usually not the reason for a small balance due unless they were incorrectly treated as taxable remuneration.

Can I avoid paying a balance next year?

Possibly, by asking payroll to withhold a small additional amount of professional withholding tax each month. This does not reduce the total tax, but it can reduce or eliminate the balance due at assessment stage.

Sources

1. FPS Finance — Tax rates — https://fin.belgium.be/en/private-individuals/tax-return/income/tax-rates

2. SPF Finances — Professional income and flat-rate expenses — https://fin.belgium.be/fr/particuliers/declaration-impot/revenus/revenus-professionnels

3. SPF Finances — 2026 tax return and simplified proposal — https://fin.belgium.be/fr/particuliers/declaration-impot/rentrer-declaration/declaration-impot

4. SPF Finances — Brussels 2026 explanatory notes — https://fin.belgium.be/sites/default/files/media/documents/explications-partie-1-bxl-2026.pdf

5. SPF Finances — Municipal tax rates 2026 — https://fin.belgium.be/sites/default/files/media/documents/taux-taxe-communale-2026.pdf

6. SPF Finances — Commuting reimbursements — https://fin.belgium.be/fr/particuliers/declaration-impot/revenus/indemnites-frais-deplacement-domicile-lieu-travail

7. SPF Employment — Meal vouchers — https://emploi.belgique.be/fr/themes/remuneration/titres-repas

8. SPF Finances — Objection to a tax assessment — https://fin.belgium.be/fr/particuliers/declaration-impot/avertissement-extrait-de-role/reclamation

This article provides a general framework and does not constitute personalised tax advice. Tax rules and deadlines can change each year, and the correct treatment depends on the taxpayer’s exact figures, documents and personal situation.

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