I'm a mechanic. I don't profit on parts, only labor. If a customer pays me with PayPal $1000 for a job, but $800 was parts reimbursement, what are the tax implications?

Specifically with regard to the new 1099K law. Will the IRS see that I got paid $1000 for this job but I only reported $200? And is this going to be a problem? I report everything anyway. Whenever someone pays me with Venmo and PayPal, I report it.