Special tax regime for inpatriate taxpayers and researchers - Clarifications provided by the Tax Administration

The Act of 18 December 2025 containing various provisions strengthened the special tax regime for inpatriate taxpayers (STRI) and for inpatriate researchers (STRIR). These amendments apply to remunerations paid or attributed as from 1 January 2025. A tax circular dated 1 April 2026 further clarified the conditions for applying these amendments and, in particular, the possible adjustments to existing employment contracts

1. Overview of the regime and new rules

The main advantage of the special tax regime for inpatriate taxpayers and researchers lies in the possibility for the employer to grant the inpatriate a lump‑sum allowance that is exempt from Belgian personal income tax and Belgian social security contributions, as reimbursement of employer-related expenses.

The amendments introduced by the Act of 18 December 2025 are as follows:

These amendments apply to remunerations paid or attributed as from 1 January 2025.

2. Divergence between tax and social security treatment

The increase of the percentage to 35% and the abolition of the cap of EUR 90,000 apply exclusively at tax level for salaried workers.

At this stage, NSSO regulations have not been amended. Consequently, the limits of 30% and EUR 90,000 remain applicable for the calculation of NSSO social security contributions for salaried workers. This divergence must be taken into account when structuring remuneration packages for inpatriate employees.

For self‑employed company directors, this divergence does not exist. INASTI social security contributions follow the taxable income base for tax purposes.

3. The allowance must be paid in addition to remuneration

A key condition of the regime is that the lump‑sum allowance must be granted on top of the inpatriate’s remuneration and cannot be included in a single global gross amount that is deemed to already incorporate the allowance.

In practice, it is therefore recommended to formally reflect this structure in the employment contract or in an addendum, clearly distinguishing the gross remuneration on the one hand and the lump‑sum allowance on the other.

4. Adjustment of existing employment contracts

The tax circular confirms that employers may adjust existing employment contracts in order to apply the new tax limits, subject to compliance with employment law, with effect at the earliest from 1 January 2025.

In practice, contractual adjustments may relate to:

• increasing the lump‑sum allowance from 30% to 35% of gross remuneration and/or abolishing the cap of EUR 90,000;
• reducing the contractual gross remuneration in order to optimise the ratio between taxable remuneration and the tax‑exempt allowance.

As regards possible retroactive amendments, these must be implemented no later than three months following the publication of the circular of 1 April 2026, i.e., by 30 June 2026 at the latest. In that case, the tax forms relating to the 2025 income year must be corrected, and amended professional withholding tax returns must be filed.

These contractual adjustments will only produce effects at the tax level: the remuneration on which NSSO contributions have already been calculated for past periods cannot be reduced retroactively.

5. Numerical illustration

The circular provides a concrete example: an inpatriate whose annual gross remuneration amounts to EUR 77,000 and who benefits from a 30% allowance (EUR 23,100).

Following a contractual adjustment applied retroactively as from 1 January 2025:

• gross remuneration: reduced to EUR 74,148.15 (NSSO contributions remain due on EUR 77,000 for elapsed periods);
• tax‑exempt allowance: 35% × EUR 74,148.15 = EUR 25,951.85 (compared to EUR 23,100 previously);
• the employer’s gross cost remains unchanged, while the tax‑exempt portion increases by EUR 2,851.85 per year.

6. Points of attention

Any amendment to an employment contract requires an addendum signed by both parties. It should be noted that a change to the gross remuneration may have repercussions on the following elements, which must be carefully assessed:

• holiday pay and end‑of‑year bonus (the impact can be neutralised if these components are included in the calculation base for the allowance);
• wage indexation (the impact can be neutralised insofar as the allowance is calculated as a percentage of remuneration);
• contributions to supplementary pension schemes (verification of contribution calculation rules in the pension regulations; verification of compliance with the 80% rule);
• variable remuneration schemes (where bonuses are calculated on gross remuneration);
• social security benefits (calculated on contribution‑liable remuneration);
• etc.

There is no legal obligation to carry out such amendments. Each case requires a case‑by‑case analysis and the agreement of both the employer and the employee.

Action point

Employers are invited to verify whether employment contracts already reflect the new tax limits (35% / abolition of the EUR 90,000 cap).

They should also identify the employees already benefiting from the STRI or STRIR within their organisation and assess the advisability of reducing gross remuneration with a corresponding increase in the tax‑exempt allowance (taking into account all related consequences and the divergence between tax and NSSO treatment).