TurboTax is unable to perform this calculation. You yourself must calculate and explicitly enter in the individual 401(k) section the amount of elective deferral you are permitted to make. Do not mark the Maximize box for an individual 401(k).
To get TurboTax to calculate the maximum permissible employer contribution, tell TurboTax to Maximize either a SEP IRA contribution or a Keogh Profit Sharing contribution. The calculation of the maximum permissible employer contribution is the same for these as it is for an individual 401(k), but these do not have elective deferrals.
