I have a small business (an LLC) that is currently taxed as a partnership. I have one partner, and we file a form 1065 for the partnership and we each get our own K-1. The income on the K-1 is listed in box 1 (Ordinary business income). I wanted to know if this income could be used to fund a Solo 401K for myself (and my partner would do the same with his K-1 income for his own Solo 401K).

Is this possible to fund a Solo 401K using business income without paying payroll taxes or having self-employment (box 14) income?

Thank you!