Update February 19, 2020. Re the articles in the Reforma Laboral from 2012, in 2015 transposed into the Statute for Employees (art. 52.d), relating to the possibility to arrange for dismissal for being absent from work as a result of being ill. A new Royal Decree, published in the State Bulletin today, coming into force as of tomorrow, the 20th of February 2020, abolishes said article in the Statute for Employees. So the text below is of historical value only.
Since the Reforma Laboral in 2012, you CAN be fired if you are absent from work, even with justification from your GP, under certain circumstances.
If you are intermittently absent from work, for 20% of the workdays in a 2 month period, and if your absent days amount to more than 5% in a 12 month period, a dismissal for that reason will be accepted by the courts as ´objective´ and thus justified dismissal.
The same goes if you have been intermittently absent due to illness for 25% of the workdays in a 4 month period.
Practival example: If you work mondays to fridays, a 2 month period would hold 45 workdays. If you have had 2 ´bajas´ in the last 2 months, amounting to 9 days in total, and you have been absent from work in the past year for more than 5% of the workdays (appr. 12, including the 9 from the last 2 bajas) your employer can justifiable dismiss you.
At the moment, employees who have been ´de baja´ as a result of a workrelated accident, or for more than 20 days, are still protected from dismissal for the reason of ´absentismo´ (being absent from work).
The only positive aspect from a ´despedido procedente´ (justified dismissal) is that your employer would have to pay you redundancy of 20 days per year you´ve worked for the company, with a maximum of 12 months.