This breaking down of one big chunk into a series of transactions under $10K is called “structuring the transaction” and it is a felony under the Bank Secrecy Act, 31 USC Section 5324. It does not matter if the money comes from a totally legal source.

What is the crime of structuring?

“Structuring” is defined as conducting one or more transactions in currency, in any amount, at one or more financial institutions, on one or more days, in any manner, for the purpose of evading reporting requirements. Many individuals bank with more than one institution and have more than one account.

What is the penalty for structuring?

So if you have $100,000 to deposit in your bank account, and you deliberately choose to deposit that money in increments of $9,999 so your bank won't automatically notify the federal government, you're guilty of structuring. It's a felony punishable by a fine and/or up to five years in prison.