At the end of the year, to help your clients, send them a nice note letting them know if they are required to report any payments they made by check to you, totaling over $600 for the year. If it's a mixed bag of check and credit card transactions, do the math for them and be nice about it. Let them know that they are not to report all of the credit card transactions they made on a 1099-NEC. If they tell you, "We have to report it," now would be an excellent time to educate them a bit more. Inform them about the hassle this will cause and the costs you might incur to remedy this with the IRS later.