Happy day...an under-50 years old client has a W2 with box 12D for $19k.  The client is a 10% owner of a partnership and the K-1 Box 14 SE income for $78k and a Sch C for $18k, so $96k combined. 

In addition to the plan he has at his W2 job, he also has an individual 401(k). 

Referring to Proseries' Keogh/SEP/Simple worksheet, I have Part I box 6f marked to compute maximum deductible contribution.  Zero is in box 6e.  The calculation seems to be allowing roughly $37k in deduction and it is carrying that to Sch 1, Part II line 15, otherwise known as the front of the return. 

I visited https://www.irs.gov/retirement-plans/plan-participant-employee/retirement-topics-401k-and-profit-sha... and the first example seems to indicate that the employer can make a non-elective contribution.  I also visited https://www.401kcheckbook.com/solo-401k-contributions-guide-2018-2019/ and it also seems to support the idea that the non-elective contribution is deductible. 

Given what I've shared, does it make sense that it is deductible?