What is the duty towards an office manager who takes money from the company for himself beyond what the office needs for maintenance, given that the amount taken is small, and informing the company owners might lead to the closure of the office or the father's dismissal from his job?

If the manager takes money for his personal needs, not for work, and the questioner's father knows about it, then he is not allowed to remain silent. He must advise him and remind him with wisdom and good admonition. If he does not respond, then he must inform the authorities responsible for him, unless he fears a definite harm to himself, such as dismissal from work. In that case, he is permitted to remain silent, while disapproving in his heart, due to the Prophet's (peace be upon him) saying: "Whoever among you sees an evil, let him change it with his hand; if he cannot, then with his tongue; if he cannot, then with his heart—and that is the weakest of faith."