Legal Question in Credit and Debt Law in North Carolina

You leave out too many facts. The best and safest answer is it depends on a whole lot of things. Did the sender and recipient know each other? Did the recipient know that the check was sent in error? Why did the recipient cash the check if they knew of the error? How much was the check for? Are you the recipient or the sender? Were both parties in North Carolina? If not, where was the other party? Does the other state's law govern? Why was the check sent in the first place?

Morally is not the same thing as legally. Even if there is no legal duty to return the funds, there might be a moral duty to do so. If you are the recipient, ask yourself not what is the legal thing but the right thing to do?

However, iIf you were the sender, there may be no recourse. For example, if you got a bill for $50 and mistakenly paid $150, the merchant might have no duty to refund the money. Most merchants might do so, but that does not alter the fact that it was your fault for sending in the $150.

In sum, I or any other attorney would need a lot more information in order to answer your question and I have not had occasion to specifically research how North Carolina would address such a question. Assuming that another state's law would apply, you might want to direct the question to a lawyer in that state but you will have to provide more details.