1. Not at all. The question and answer in this thread applies specifically to the case where an individual makes elective deferrals or Roth contributions to both an individual 401(k) and a 401(k) at a separate employer.
2. The Maximize box causes TurboTax to calculate the maximum permissible contribution by completing the calculations in the Deduction Worksheet for Self-Employed in IRS Pub 560, a worksheet that only applies to an individual who participates in only one defined contribution plan. If TurboTax is calculating a higher deductible amount than the amount you explicitly entered, it means that your combined employee elective deferrals and Roth contributions plus your employer contribution are less than the permissible maximum. By marking the Maximize box you are also telling TurboTax that you will be making all of the contributions necessary to allow the maximum deduction and that you have made no employee contributions for the year to another employer's plan.
3. The self-employed retirement deduction appears on line 15 of Schedule 1.
