All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
The ruling on your father evading taxes and customs fees depends on the kind of the taxes which are imposed; if these taxes are of the forbidden kind that are unjustly taken, or which are taken to be spent on what is forbidden, then it is permissible for your father to evade them and avoid paying them if this does not cause harm to others. But if these taxes are lawful, then it is not permissible for him to do so as we clarified in Fataawa 86837 and 89947.
Besides, you should not be shy of advising him in a good and gentle manner without argumentation and without raising your voice, as your advising him is an act of being kind and dutiful to him.
Indeed, the responsibility of enjoining good is an obligation even on a disobedient person as he is himself obligated to act according to the good and enjoin others to do so, and being negligent in one of these two obligations does not mean that one is exempted from doing the second obligation. Of course, a person who acts according to what he enjoins is more likely to influence other people.
On the other hand, abandoning the prayer and being negligent in performing it is one of the great major sins as we clarified in Fatwa 84235. So, you should take the initiative to repent to Allaah from this and from the other sins like cheating and the like, as whoever sincerely repents, Allaah accepts his repentance. For more benefit on the conditions of repentance, please refer to Fatwa 86527.
Allaah Knows best.