I'm working in Europe for a big multinational company. I was promoted last year, with an increase on my base salary and bonus.
I recently received my bonus for last year. However my company just told me they made a mistake with the calculation, as they paid me my new bonus instead of a pro-rata based on the number of months I worked respectively on my previous and new position. It resulted in what they say is a higher bonus than what they intended to pay.
Now I am not aware of any internal document that details the bonus calculation or what happens to the bonus in case of a mid-year promotion, so I'm a bit puzzled by the issue and unsure if the mistake is legitimate or some a posteriori optimization attempt. Can they take my bonus back, or at least in part?
Edit: my contract does not define any kind of bonus structure.