In the cases of international employees, what do I have to do with what has been withhold and reported until the start/end of the assignment?

In the case of employees with international mobility, the employee can change his/her residence status and one tax or another may be applicable.

In these situations, procedures to be carried out before the Social Security or the Tax Authorities may also change.

The Company must be prepared and know how to regularize the withholdings of taxes and Social Security, as well as the possible procedures to fulfilled by the employee at departure/arrival.