Transactions $10,000 or more per day trigger an automatic currency transaction report (CTR) to the Treasury Department FinCEN that the IRS has access to. Keeping the amounts below that figure and staggering payments will keep you under the radar.
However, don’t do anything stupid like conducting transactions of $9,990 today and $9,990 tomorrow. Also crazy would be $500 today and $500 tomorrow. Keep transactions well under $10,000 and make them very infrequently — such as two or three times per month. Or even less.