Many foreign companies find themselves in serious trouble with the Spanish Employment Courts after they have fired an employee. In Spain, to fire un employee has a legal right to appeal his dismissal in court. The courts with then qualify the dismissal as fair, unfair or void.
For a European posted worker or expat, it is possible to be under two different tax jurisdictions at the same time. If their earnings come from two or more countries, they could owe two different national taxes.
If you are planning a collective redundancy, you must begin consultations with staff representatives in advance. During the consultation with staff representatives you should discuss different options to avoid the lay-off, or at least to reduce the number of staff affected.