I would take it back. But on one occasion I was at the bank and I cashed my work check. I stepped to the side and recounted it and found out that the teller gave me $100 extra. I got back in line and told her that she had made a mistake. She said I Don't MAKE MISTAKES...... With that I turned and walked away and kept the money. I am sure that at the end of the day she would eat her words.