Attached is Publication 560 (2022), Retirement Plans for Small Business which gets into the details of calculating income for self-employed individuals.
There is a worksheet titled Deduction Worksheet for Self-Employed with Step 1 is:
Enter your net profit from Schedule C (Form 1040), line 31; Schedule F (Form 1040), line 34;* or Schedule K-1 (Form 1065),* box 14, code A.** For information on other income included in net profit from self-employment, see the Instructions for Schedule SE (Form 1040)
Note that Schedule E is not listed along with the other schedules, and many of income items on Schedule have to do with passive income. It is worth looking at the Schedule SE instructions where there are long lists of what is and is not included in earnings from self-employment.
If you distill all of this down, any income on Schedule E that is considered as income from self-employment for personal services would be reported on the individual's K-1.
Any income reported solely on Schedule E is insufficient to determine if that income should be considered by a retirement plan. If the Schedule E income does not flow through to Schedule K-1 or to Schedule SE, then it is not income from self-employment and should not be used for retirement plan purposes.
If the client believes it should be included, or the TPA believes it should be included, then the burden of proof is on them.
p560.pdf