What is the ruling on a mother working as an accountant for employee salaries at the Egyptian Post Authority, which includes permissible and prohibited activities, knowing that she calculates everyone's salaries and has no direct involvement in usurious activities?

Your mother is not permitted to calculate the wages of workers involved in forbidden activities if these wages are due for such forbidden work, because her action would then be an affirmation of the unlawful and an assistance to it. Allah Almighty has said: "And do not cooperate in sin and aggression." Therefore, your mother must leave her work in the aforementioned department.