The Qualified Business Income Deduction will be calculated once all of your income tax data has been entered into your return.
If you do have a deduction, this will be reflected on line 9 of your 1040 return.
TurboTax also uses Qualified Business Income Deduction worksheets in the software which are created from data you enter in order to determine and calculate the Qualified Business Income Deduction.
Here is more information for you related to this deduction:
https://ttlc.intuit.com/replies/7019998
Here is a link to contact TurboTax if your issue continues:
[Edited 1-16-19|4:26PM]
