Circular letter letter confirms retroactive application of expanded expat regime

1. Expansion of the expat regime 

The changes introduced at the end of 2025 are as follows: 

For both inbound taxpayers and researchers: 

• The tax-free expat allowance may amount to a maximum of 35% of the annual gross salary (previously 30%).  
• The cap of EUR 90,000 for the tax-free expat allowance has been abolished.  

Specifically for inbound taxpayers: 

• The minimum annual gross remuneration is reduced from EUR 75,000 to EUR 70,000.  

For the year of arrival in Belgium, as well as for the year of departure or the year in which the expat regime ends, a pro rata calculation of the thresholds of EUR 90,000 and EUR 75,000 previously applied. 

The circular letter of 1 April 2026 now clarifies that: 

• The minimum annual gross remuneration is calculated pro rata based on EUR 70,000 (instead of EUR 75,000).  
• The pro rata calculation of the maximum amount of EUR 90,000 is abolished due to the removal of the cap.  

The tax authorities do not address the position of the National Social Security Office (RSZ/ONSS), which does not follow the expansion of the expat regime (except for the EUR 70,000 threshold, which it has indicated it will follow). For social security contributions, however, the pro rata calculation of the EUR 90,000 cap remains relevant. This discrepancy between tax and social security treatment leads to practical difficulties and uncertainty. 

2. Entry into force

The legislative changes relating to the expanded expat regime apply retroactively to remuneration paid or granted as from 1 January 2025. 

Regarding this retroactive effect, the circular letter distinguishes two situations: 

1. Employees already subject to the expat regime 

The tax authorities clarify that employers may adapt existing employment contracts to the expanded expat regime. For example, they may retroactively reduce the gross salary and increase the tax-free expat allowance from 30% to 35%. 

The circular letter emphasizes that such changes may have secondary effects (such as lower pension rights or holiday pay) and recommends taking these into account. 

According to the circular letter, retroactive changes to employment contracts can be made until 30 June 2026. The consequences of changes made after this date remain unclear. 

In addition, the circular letter only refers to employees, although it appears evident that the same changes should also apply to company directors. 

2. Employees/company directors not meeting the EUR 75,000 threshold 

For employees and company directors with a gross remuneration between EUR 70,000 and EUR 75,000 before 10 January 2026, an extended deadline to apply for the expat regime applies until 9 April 2026. 

Normally, this deadline is three months from the start of employment. Those who have been in this situation since 1 January 2025 may therefore still submit an application in time. 

The circular letter specifies, however, that this exceptional deadline applies only to this specific case and not to other late applications. 

3. Action? 

The circular letter confirms that the expanded expat regime can be applied retroactively. Existing remuneration structures can be adjusted accordingly as from 1 January 2025. 

Companies, employees and company directors already applying the expat regime should therefore verify whether their current remuneration packages have been aligned with the recent changes. Tiberghien will of course be pleased to assist you in this regard.