retirement age

I think there is a special status for people who have reached retirement age. This means you pay less social security contributions. But you may need to check this with Liantis (my business desk).But you will have to pay a lot of personal income tax. You already have your pension, which pushes you into the higher personal income tax brackets, and then you have your self-employed activity on top of that, so you immediately end up in the higher brackets.

Anyway, it's no different than if you were still working and then started a secondary occupation :) It's the same system there.