Is money that a person obtains as a result of an administrative error by other parties considered permissible or forbidden, and must it be returned?

You do not own what came to you as a result of an administrative error. You must return it to the responsible party, because unlawful wealth is not permissible to own; rather, it must be returned to its owner. The Messenger of Allah, peace and blessings be upon him, said: "The feet of a servant will not move on the Day of Resurrection until he is asked about four things: about his life and how he spent it; about his youth and how he wore it out; about his wealth, from where he acquired it and in what he spent it."