TurboTax does not appear to have any problems calculating the proper actual employer contribution outside of the fact that the elective deferral and catch-up limits have not yet been updated. The ability to make an employer contribution depends on your net earnings from self-employment. If all of your net earnings go to elective deferrals, nothing remains to fund the employer contribution. Also, your employer contribution is limited to 20% of net earnings or one-half of the amount of net earnings that remain after subtracting your elective deferrals, whichever is less. You can review the calculation on TurboTax's Keogh, SEP and SIMPLE Contributions Worksheet.
Net earnings are your net profit minus the deductible portion of self-employment taxes.
Since you appear to be using the CD/download version of TurboTax, in forms mode you can override and correct on the Keogh, SEP, and SIMPLE Contributions Worksheet the amounts on lines 9, 17 of Part III and line 1 of Part V. You'll need to remove those overrides once the worksheet is corrected by TurboTax. It would be best to do these overrides in a copy tax file separate from the one that you use to prepare the tax return that you will actually file.
