If you've been dismissed or think it might happen, it matters which type of dismissal applies to your case, because it determines the compensation (if any) and whether you can challenge it. Spain has several categories, each with different financial consequences.
Disciplinary dismissal
This is when the company justifies the dismissal with a serious, culpable breach by the employee (repeated unjustified absences, insubordination, offensive conduct, a drop in performance, etc.). If the dismissal is ruled fair (the company proves the cause), there's no compensation. If it's ruled unfair (the cause isn't proven or there's a procedural defect), the company must choose between reinstating the employee or paying compensation of 33 days' salary per year worked, capped at 24 months' salary (for contracts signed after the 2012 labour reform; earlier contracts keep a mixed, more favourable calculation for years worked before the reform).
Objective dismissal
Based on economic, technical, organisational or production-related causes at the company, or on the employee's supervening unsuitability, among other causes defined by law. If ruled fair, compensation is 20 days' salary per year worked, capped at 12 months' salary. It must also be communicated in writing with at least 15 days' notice (or those days must be paid if notice isn't given).
Collective dismissal (ERE)
An objective dismissal affecting a minimum number of employees within a set period (which varies by company size), requiring a special procedure with a consultation period with employee representatives. The legal minimum compensation is also 20 days per year with the same 12-month cap, though collective bargaining commonly secures higher amounts.
Void dismissal
Declared void when it violates fundamental rights (for example, if it's discriminatory, or affects a pregnant employee or someone on maternity/paternity leave without sufficiently proven justified cause). The consequence is mandatory reinstatement of the employee with back pay for wages lost; the company cannot choose compensation instead.
Resigning: not a dismissal
If you're the one who decides to leave, there's no dismissal compensation (it isn't a dismissal), though you're still entitled to be paid the proportional amounts owed (untaken holidays, prorated bonus payments). You must respect the notice period set by your contract or agreement, typically between 15 days and a month.
What to do if you disagree with your dismissal
You have 20 working days from notification of the dismissal to file for conciliation and, if there's no agreement, a claim before the labour court. That deadline is short and can't be extended, so it's worth acting quickly if you think the dismissal was wrong.