At the end of the year our department head calculated our bonuses and based on that we received our annual bonus. I accidentally found out that my bonus was exactly half of what my colleagues...

I would ask how bonuses were determined and what you can do to increase the probability of achieving a higher bonus in the future. I would also have a... list of the impacts I made in the company to provide evidence that hopefully lines up with the criteria. I would ask for a specific rubric or criteria to ensure that you are working in alignment with the company's expectations and priorities so that you know how to manage your efforts and time. Let that determine how you proceed. I once had a staff of mine who thought his evaluation was unfair (it determined raises) and he requested a meeting to get more clarity. I was able to show him what high achievers' impacts looked like and he couldn't argue with the decision after that. It changed the way he showed up and I was happy to support him in getting to a high impact status in the organization.  more