Assalamu Aleykom wa rahmatullah wa barakatuh Ustaadh, Once again about doing the bookkeeping of my father who is a taxi driver. If I am sure that he has some rides that includes bringing to places where is music and stuff, such as concerts or festivals. Is it still allowed to do the bookkeeping?

‎Keeping your father's general books is allowed, because his work is permissible and the sin of a forbidden ride is on him, not you. What you must not do is help with the forbidden part itself, like arranging those specific rides. Advise him gently that knowingly driving people to concerts is not allowed.