Utilize your financial knowledge, give your answer or opinion to the input question or subject . Answer format is not limited.

Why would you ever turn down a raise in salary?
Here in Germany there is a special case. I am studying (and working a little on the side) and still receiving child benefits from the state which is like 190€/m. Because I am getting this I don't have to pay tuition which is 1k/y. If my side income would get over the boundary (which is like 9k/y) I would lose those benefits (~3.3k) and would have to pay insurance myself (I dont know how much that would be. 50-100/m I guess.) So getting a raise from 8k to 10k sounds nice as it is a 25% raise, but it actually means getting less.