If a company makes a mistake and sends an extra item you didn t order, you have an ethical obligation to return it, but legally, you don t have to send it back.
It s yours to keep.
As Consumerist points out, The Federal Trade Commission FTC explains the rules fairly clearly.
According to the FTC website:
What do you do when you receive merchandise that you didn t order?
According to the Federal Trade Commission, you don t have to pay for it.