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.
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.