Even taking 10k in chips the casino, is required to file a Book Wagering Report, which is a gaming comission requirement held at the state level. However the IRS has access. The casino will still ask for your social to fill out a BWR. You technically can refuse it for this purpose, but the books will usually balk at you for doing so. I've even had books threaten not to pay me for refusing to give a SSN for a BWR only(non-ctr) type transaction, even though the state instructions on filling out a BWR clearly say the patron can refuse...