First of all, you have to be engaged in a trade or business and have received the cash in the course of that trade or business.
Also, review the definition of "cash" for reporting purposes.
The term “cash” means the following.
• U.S. and foreign coin and currency received in any transaction; or
• A cashier’s check, money order, bank draft, or traveler’s check having a face amount of $10,000 or less that is received in a designated reporting transaction (defined below), or that is received in any transaction in which the recipient knows that the instrument is being used in an attempt to avoid the reporting of the transaction under either section 6050I or 31 U.S.C. 5331.
