With dismissals, companies do not always behave in accordance with the regulations in force and it is necessary to appeal to the courts for the Judge to decide whether a dismissal and its corresponding compensation have been correct. The first thing we advise is that the dismissal letter be signed as "not compliant", this signature only indicates that you are aware of it.
In the event that the dismissal occurs for objective reasons according to the company, compensation must accompany the dismissal letter. That compensation must be 20 days per year of service. Your acceptance does not indicate that you are happy with the dismissal.
If the company imputes a very serious fault the worker will not pay any amount for compensation. It would be the court that should establish it in case of coming to trial. The term to file a claim for dismissal is 20 days.