Hi Team!  I have a quick Solo 401(k) Question. 

I have a client with an individually owned S-Corp and he is the only owner and employee.

My understanding is that the employEE can first make a employee contribution for up to $21,000 (in 2022) before year end.  My question is, is remaining employER contribution limited to 25% of his remaining wadges?  Or is it 25% or total business income?

For example, if the business makes $300,000 of gross income, the employee takes a salary of $100,000.  Is it that he can make an employee contribution of $21,000 and then take 25% of the remaining $79,000 or his wadges?  or is it 25% of his business net income?