What is the ruling on an employee accepting a gift (money or otherwise) from his manager at work, if the company is state-owned?

If the gift is from the giver's personal money, there is no harm in accepting it. However, if it is from company funds without permission, it is not permissible to accept it. Similarly, it is not permissible to accept a gift if it is a bribe for cheating or deception, as it falls under the scope of forbidden bribery, the perpetrator of which the Prophet, peace and blessings be upon him, cursed.