There is no place that you need to enter the plan rate itself. If you mark the Maximize box in TurboTax for a SEP plan, TurboTax assumes the maximum permissible base plan rate of 25% which works out to the maximum permissible SEP contribution for the self-employed of 20% of net earnings. (Net earnings = net profit minus the deductible portion of self-employment taxes.) Any contribution less than the maximum permissible implies a base plan rate of less than 25%. If you make a SEP contribution of less than the maximum permissible you simply enter the amount contributed and do not mark the Maximize box; it doesn't matter what the plan rate actually works out to unless you have eligible employees for whom you also must make SEP contributions.
