Thank you for your response.  

The 2022 returns were filed on time in April 2023.
Actually, the client just sent me the CP2000 for her 2022 return. The IRS assumed that the income had not been reported at all. I had originally reported the 1099-NEC income as part of her taxable scholarship & fellowship income which was reported as other income not subject to SE tax on the tax return. I thought that was the proper treatment. 

This amount was not part of a fellowship and was categorized by the Institute as an honorarium.

The IRS shows the 1099-NEC amount as SE income.  She also had excess advanced premium tax credit which would have been increased if the income had not been reported at all. The amount including interest would have been over $1,000.

So the question comes down to whether or not the 1099-NEC income is subject to SE tax. If not , how do I support my position that it is not?