If I want ProConnect Tax to calculate the maximum Solo 401(k) employer and employee contributions for a sole proprietor, do I enter 1 in the Profit-sharing (25%/1.25) (1=maximum) field and 1 in the Total SE elective deferrals (except Roth) (1=maximum) field as shown below?

Can you explain when to use the Profit-sharing (25%/1.25) (1=maximum) field versus the Self-employed SEP (25%/1.25) (1=maximum) field? 

Test it yourself by putting an income on Sch higher than the maximum needed to maximize the deduction. Then you will learn which to use.

I don’t understand your reply.

I think Accountant Man was answering this:

"Can you explain when to use the Profit-sharing (25%/1.25) (1=maximum) field versus the Self-employed SEP (25%/1.25) (1=maximum) field?"

Anyway, a 401(k) is not a SEP. A 401(k) is a type of Profit Sharing Plan.

Enter a Sch C with $300,000 of profit. Then click a box or whatever to calculate the maximum allowed.