As there are (possibly) employees of yours travelling for work, it is important to know that depending on the frequency, this could trigger tax residency in that country. In addition, the individual taxation of the income related to these business travel days should be further investigated. This may vary depending on the applicable (special) tax status and the bilateral double tax treaty concluded between the working state and the residence state and whether a specific COVID-19 agreement between Belgium and the neighbouring countries (as the normal working state) can be applied for i.e. The Netherlands/France/Luxembourg/Germany.
Just contact us if you would like some help with verifying or determining if this is applicable to your situation.