Is one sinful if he does not inform his father of a large sum he received from his company's profits, despite his father's need for this money?

A son is not required to inform his father about the money he earns. He has the right to possess and dispose of his money without his father's knowledge. The Hadith: "You and your wealth belong to your father" means that it is permissible for the father to take from his son's wealth when in need, not that the father owns it. The son's wealth is his own property; he is obligated to pay zakat on it, and it is inherited from him. The majority of jurists hold that a father may take from his son's wealth if he is in need. The Hanbalis, however, hold that a father may take from his son's wealth absolutely, subject to conditions: that he does not cause hardship or harm to his son, and that he does not take it to give it to another child.