What is the ruling on working fewer hours than officially designated in a government job, given that this does not affect the work, and is it permissible to donate the difference in working hours as charity?

It is not permissible for an employee to leave during working hours or to be late without permission from the one authorized to grant it, in accordance with the Almighty's saying: (O you who have believed, fulfill [all] contracts), and the Hadith: "Muslims are bound by their stipulations." Whoever violates this is not entitled to their full salary except for the amount corresponding to the work they performed. The entity is permitted to deduct the corresponding amount from their salary, and the employee must return what they took without right. If returning it is not possible, they should give it in charity.