Is it permissible for an employee to accept a gift after helping a contractor complete a transaction outside the scope of his official duties?

It is not permissible for an employee to work for an entity other than their employer during official working hours, nor is it permissible for them to accept gifts offered to them by virtue of their position unless authorized by their employer. As for a gift given in exchange for a service or intercession outside of work, there is no harm in accepting it. It must be noted that it is not permissible for a Muslim to intercede for another to obtain something that is not rightfully theirs. If they do so, then the gift is a prohibited bribe that must be spent on the general welfare of Muslims.