The tax agreement that Belgium concluded last year was valid until June 30, 2021. An employee’s professional income is usually taxed in the country where he or she is employed (with certain exceptions). However, due to the coronavirus crisis, many employees can no longer cross the border to work abroad for their employer. As a result, these employees are no longer taxable in the country of regular employment, but in their country of residence.

However Belgian has concluded specific agreements with neighbouring countries so that the employee is taxed in Belgium as if he or she was in Belgium until September 30. This applies to French, Luxembourg, Dutch and German employees who are currently forced to work from home due to the coronavirus.

Source

SDWORX