Annoyingly, such changes are often not implemented until an update release sometime in December, despite the updated limit having been announced by the IRS more than a year earlier. Until the limit is corrected in TurboTax, you can use overrides in forms mode on the Keogh, SEP and SIMPLE Contribution Worksheet. You'll need to override Part III line 8 to have $54,000, then override Part V lines 1 and 2 to apply the result calculated on Part III line 21, if different.
Be aware that if you override the lines in Part V, you'll need to manually update those amounts each time you make a change to your SE profit that results in a change to the amount calculated on Part III. You'll also need to removing the override in Part III each time you update TurboTax, checking to see if the limit has been corrected.
Are you using the 2017 software, and have you run an update?
Annoyingly, such changes are often not implemented until an update release sometime in December, despite the updated limit having been announced by the IRS more than a year earlier. Until the limit is corrected in TurboTax, you can use overrides in forms mode on the Keogh, SEP and SIMPLE Contribution Worksheet. You'll need to override Part III line 8 to have $54,000, then override Part V lines 1 and 2 to apply the result calculated on Part III line 21, if different.
Be aware that if you override the lines in Part V, you'll need to manually update those amounts each time you make a change to your SE profit that results in a change to the amount calculated on Part III. You'll also need to removing the override in Part III each time you update TurboTax, checking to see if the limit has been corrected.
The current version of 2017 TurboTax does use the correct value of $54,000 for the regular contribution limit on line 8 of Part III of the Keogh, SEP and SIMPLE Contribution Worksheet, so no need to override that. However, it's still using $53,000 for the regular contribution limit on lines 1 and 2 of Part V, so overrides will still be needed there until an update fixes the problem.
The text on Part III line 8 has not yet been updated, but that often does not happen until the form is approved for filing.
Today's release (R7) corrects the problem. Update your software to obtain the fix and be sure to go back and remove the overrides.