How should a Belgian resident declare Dutch salary in the 2025 income year / 2026 assessment year?
How should a Belgian resident declare Dutch salary in 2025? Usually in Belgium as foreign salary exempt with progression, depending on facts.
A Belgian tax resident who works in the Netherlands must normally declare the Dutch salary in the Belgian tax return, even if the income is usually exempt from Belgian federal tax under the Belgium–Netherlands tax treaty. The salary is generally reported as foreign professional income exempt with progression, but the correct treatment depends on the exact work location, treaty position and personal situation.
The figures below are illustrative and relate to income year 2025 / assessment year 2026.
Why Dutch salary must still be declared in Belgium
Belgian tax residents must declare their worldwide income in Belgium. This includes salary earned abroad, even where a double tax treaty gives another country the right to tax that income.
For Belgian residents working in the Netherlands, the key rule is that employment income is generally taxable in the country where the work is physically performed. If the work is carried out in the Netherlands, the Netherlands will usually have the primary taxing right.
That does not mean the salary can simply be ignored in Belgium. Belgium generally requires the Dutch salary to be declared because it can affect:
the Belgian tax rate applied to other income;
the calculation of the household’s Belgian tax position;
possible municipal or agglomeration tax effects;
the correct application of treaty exemption.
This is why a Dutch salary may need to appear in the Belgian return even if it is not taxed again as ordinary Belgian salary.
What if Tax-on-web does not prefill the Dutch salary?
Foreign salary is often not automatically prefilled in Tax-on-web. The absence of prefilled information does not mean there is nothing to declare.
A Belgian resident who received Dutch employment income should manually check whether the income must be entered in the Belgian return.
This is especially important where the person has:
a Dutch annual salary statement;
Dutch wage tax or payroll withholding;
a Belgian tax residence during the income year;
a Belgian partner or joint tax return;
foreign bank or investment accounts linked to the Dutch situation.
Where to enter Dutch salary in the Belgian tax return
In many Belgian tax return situations, Dutch employment income must be reported in two steps.
First, the salary is entered in the normal employment income section of Box IV / Cadre IV. For ordinary employee salary, the relevant paper codes are generally:
1250-11 for the first taxpayer column;
2250-78 for the second taxpayer or partner column.
The salary should be entered under the correct taxpayer’s name, not under the partner’s name.
Because there is usually no Belgian fiche 281.10 for Dutch salary, the income should be entered in the section for salary that does not appear on a Belgian fiche, or the equivalent foreign employment remuneration section in Tax-on-web.
Second, the income should also be repeated in the foreign income section of Box IV, section O. For Dutch employment income that is exempt in Belgium under the treaty but taken into account for progression, the relevant section is normally Box IV, O.2.
In practical terms, the foreign income section should indicate:
Country: Netherlands;
Code: the same salary code used in Box IV, usually 1250-11 or 2250-78;
Amount: the Dutch employment income amount used for Belgian reporting.
What amount should be declared?
For income year 2025, an illustrative Dutch annual statement could show:
Dutch taxable salary: €55,003;
Dutch wage tax / payroll withholding: €14,321;
net foreign professional income for Belgian reporting: €40,682.
The logic is that foreign professional income may be taken into account in Belgium at its net amount: gross foreign salary less foreign tax and statutory social security contributions withheld at source.
In that example, the Belgian return would generally use €40,682 as the Dutch employment income amount, unless Tax-on-web specifically asks for a different breakdown, such as gross income and foreign tax separately.
The Dutch wage tax should not be entered as Belgian précompte professionnel. Dutch payroll withholding is not Belgian withholding tax.
What should not be entered separately?
Some Dutch items may appear on a Dutch annual statement or tax file but should not automatically be inserted into the Belgian return as separate Belgian deductions or income.
For example:
Dutch wage tax should not be reported as Belgian withholding tax;
Dutch arbeidskorting should not normally be entered separately in the Belgian return;
employer-side Dutch social insurance or Zvw contributions should not normally be treated as the worker’s personal Belgian deductible expenses.
The Belgian return should focus on the correct Belgian reporting of the Dutch employment income and the treaty exemption mechanism.
Effect on a Belgian partner or joint return
If the taxpayer is legally cohabiting or married, the Belgian tax return may be a joint return, depending on the timing and Belgian tax rules.
The Dutch salary should still be identified under the person who earned it. It should not be mixed with the Belgian salary of the other partner.
Correct reporting matters because foreign exempt professional income can influence the Belgian calculation. For example, if the Dutch salary is omitted, Tax-on-web could incorrectly treat one partner as having no professional income, which may affect household mechanisms such as the marital quotient.
If Belgian tax remains due after entering the Dutch income, that does not automatically mean Belgium has taxed the Dutch salary twice. The remaining Belgian tax may be caused by:
exemption with progression;
local tax effects;
the joint-return calculation;
other Belgian income in the household.
Telework from Belgium: why work location matters
For cross-border employment income, the physical work location is crucial.
If the work is physically performed in the Netherlands, the Netherlands usually has the taxing right. But if part of the work is physically performed from Belgium, Belgium may have taxing rights over that corresponding part of the salary.
There is no general treaty rule saying that small amounts of Belgian telework can always be ignored. If Belgian telework is genuinely occasional, such as a few hours per month, the practical risk may be limited, but the situation should still be documented.
A simple work-location calendar can be useful. It should record:
days worked in the Netherlands;
days or hours worked from Belgium;
any regular telework pattern;
changes in work arrangements during the year.
If Belgian telework becomes regular or substantial, the salary may need to be split between Dutch-taxable and Belgian-taxable workdays.
Social security and cross-border telework
Income tax and social security are separate issues, but both can be affected by cross-border telework.
For EU social security purposes, substantial work in the state of residence can create consequences. A commonly relevant threshold is 25% of working time in the state of residence. Under the EU cross-border telework framework, continued social security coverage in the employer’s state may sometimes remain possible where telework in the residence state stays below 50%, subject to conditions and a formal request.
A few hours of Belgian telework per month will often be below these thresholds, but it should still be monitored.
Special attention for university, teaching or research roles
Where the Dutch employer is a university or educational institution, an additional treaty point may need to be checked.
The Belgium–Netherlands tax treaty contains a specific rule for certain education situations. In some cases, professors, teachers or scientific researchers may be taxable in the country of residence for a limited period, depending on the treaty conditions.
This does not automatically apply to every employee of a Dutch university. Administrative, technical, operational or other non-covered roles may remain under the ordinary rule: taxation in the country where the work is physically performed.
Where the role involves teaching or scientific research, the treaty position should be reviewed carefully before submitting the Belgian return.
Foreign bank and investment accounts
Dutch employment situations often involve Dutch bank accounts, savings accounts or investment accounts. For Belgian tax residents, these can create a separate Belgian reporting obligation.
A Belgian resident must generally declare foreign bank accounts and foreign securities accounts in the Belgian tax return, even if:
there was no income from the account;
the account was held only briefly;
the account is only used for salary payments;
the account is with a foreign neobank or broker.
Foreign accounts must also be reported once to the Belgian Central Point of Contact, often referred to as the PCC or CAP, unless they have already been reported before.
This obligation is separate from the question of how the Dutch salary itself is taxed.
What about an earlier Belgian assessment showing no tax due?
A prior Belgian tax assessment showing €0 does not necessarily prove that foreign salary never had to be declared.
If a person became Belgian resident during a year and earned Dutch salary after becoming Belgian resident, the Dutch salary may still have had to be mentioned in Belgium as foreign employment income exempt under the treaty.
In some cases, the Belgian tax effect may be limited or nil, especially where there is no other Belgian income or where the joint-return rules are not yet fully applicable. But the reporting obligation can still exist.
For a full year of Belgian residence, such as income year 2025, the position is clearer: Dutch salary should generally be manually added to the Belgian return if it is not prefilled.
Practical checklist before submitting the Belgian return
Before submitting a Belgian return involving Dutch salary, check the following:
The Dutch salary is entered under the correct taxpayer’s name in Box IV.
The salary is entered using the appropriate employment income code, usually 1250-11 or 2250-78.
The same income is repeated in Box IV, section O.2 as Dutch income exempt with progression.
Dutch wage tax is not entered as Belgian précompte professionnel.
Any Belgian partner’s salary remains under the partner’s own name.
Foreign bank, savings or investment accounts are declared where required.
The Dutch annual statement, Dutch tax assessment, employment evidence and work-location calendar are kept as supporting documents.
Frequently asked questions
Do I have to declare my Dutch salary in Belgium if I already paid tax in the Netherlands?
Yes. A Belgian tax resident normally has to declare worldwide income, including Dutch salary. The salary may be exempt from Belgian federal tax under the treaty, but it can still affect the Belgian tax calculation.
Which Belgian tax code is used for Dutch employment income?
For ordinary employee salary, the Belgian paper codes are generally 1250-11 for the first taxpayer column and 2250-78 for the second taxpayer or partner column. The same income is then usually repeated in Box IV, O.2 as foreign income exempt with progression.
Should Dutch wage tax be entered as Belgian withholding tax?
No. Dutch wage tax or payroll withholding is not Belgian précompte professionnel and should not be entered as Belgian withholding tax.
Does Belgian telework change the tax treatment of Dutch salary?
It can. Employment income is generally taxed where the work is physically performed. If part of the work is performed from Belgium, Belgium may have taxing rights over that part of the salary.
Does a Dutch bank account have to be declared in Belgium?
Usually yes, if the person is a Belgian resident. Foreign bank, savings and securities accounts must generally be mentioned in the Belgian tax return and reported once to the Belgian PCC/CAP, unless already reported before.
Is Dutch salary automatically prefilled in Tax-on-web?
Not always. Foreign salary is often not prefilled, so the taxpayer may need to add it manually.
This article provides a general framework and is not a personalised tax opinion. Tax rules and administrative practice can change yearly. The correct treatment depends on the exact work location, treaty position, income documents, household situation and foreign account details.
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