Circular letter on the tax exemption for (continuous) shift work ‘bis’ clarifying the application in case of shifts of variable size

On 30 July 2025, a Circular letter (2025/C/50) was published with further guidance on how to calculate the correction factor when applying the alternative application of the tax exemption for (continuous) shift work (also referred to as the ‘bis’ application).  This update is important for companies applying the withholding tax exemption for shifts of variable size.

The alternative application allows the exemption to be applied in case the size of the work between succeeding shifts is not the same. In this case, the exemption should be reduced by a “correction factor” to reflect the difference in size between the successive shifts. For more information on the alternative application, please see our previous Tax Alerts of 25 March 2024, 16 May 2024 and 23 January 2025.

The circular letter refers to the shift work definition, the threshold as of when the alternative application should be applied and includes a number of examples as to explain how the correction factor should be calculated in specific cases.

Shift work definition

Shift work requires collaboration in executing the same task. This is different from individual tasks performed simultaneously by employees.

Employees performing the same work that are considered as a shift according to the fiscal definition of shift work should not be artificially divided into smaller groups to maximise the tax exemption, as this is considered fiscal abuse. Determining a shift requires assessing the actual situation, including the applicable work regulations and processes to determine the work schedules.

Threshold

The fiscal administration allows a difference in the size of the work   between successive shifts up to 10%, calculated as follows: the difference between the number of employees in the largest shift and the number of employees in the smallest shift divided by the number of employees in the largest shift.

This difference in work size of 10% is assessed day by day and per shift system.

If the difference in work size doesn’t exceed 10% for each working day of the month, the employer may apply the standard application for (continuous) shift work that month.

However, the employer is free to apply the standard application, in case it can be demonstrated that the higher deviations in the number of shift members result from circumstances beyond his control.

Once the employer chooses the ‘bis’ application, the 10% tolerance for the calculation of the exemption is no longer applicable. Any deviation effects the correction factor.

Concrete examples

The circular letter contains some practical examples on when to apply the ‘bis’ application and how to calculate the correction factor when applying the ‘bis’ application for (continuous) shift work.

We have summarised some important (non-exhaustive) considerations :

• The Circular letter confirms that there can only be one overall correction factor for the ‘bis’ application. This is important for companies with multiple shift systems operating under the ‘bis’ application. It is not allowed to apply the correction factor separately for each system.

• The correction factor of the ‘bis’ application is applied to the available wage withholding tax if that amount is lower than the theoretical exemption of 22.8%.

• For each employee, the one-third norm condition (i.e. minimum 1/3 of working time during the month must be performed in shift/night) must be calculated separately for each tax exemption. In case the employee has performed both classic shift work and continuous work during the month, the one-third norm is calculated considering both the hours worked in classic shifts and the hours worked in continuous shifts during that month. The same counts for the hours worked in classic shifts ‘bis’ and the hours worked in continuous shifts ‘bis’.

• If for a particular employee both the one-third norm for the standard application and ‘bis’ application are met, then the employer must choose one of these exemptions.

• In case of a two-shift system, one qualifying for the standard application and one for the ‘bis’ application, the employer can opt to apply the ‘bis’ application to both shift systems.

• In case of a three-shift system, the employer may choose between (1) exclude the night shift: applying tax exemption for night work and shift work ’bis’ (difference in work size between early-late shift) separately or (2) include the night shift: applying shift work ‘bis’ on the three shifts (difference in work size across all three shifts). The choice is closely related to reaching the one-third norm.

For income year 2024, corrections with respect to the tax exemption for night work, shift work (bis) and continuous shift work (bis) are still possible via Finprof until 19 September 2025 (NL | FR).