I have had occasional trouble in the past with $100 bills from a casino being rejected by an ATM. I always just presumed that it was because the bill itself was tattered or had been marked upon (why someone would doodle on a $100 is beyond me). Never occurred to me that it might be counterfeit. In the most recent instance, it was a bill I had received from a jackpot hand pay in Vegas. After the ATM kicked it back I noticed that it had some handwriting on it, so just used it to buy some groceries at a local supermarket. I hope the Feds don't come calling!