After you file

If you reported self-employment income, and TurboTax determined that you were eligible for QBI based on the information you entered, then it calculates the deduction for you.  

Before you do anything, try searching for QBI, using the magnifying glass, and typing QBI. ‌Also review your return to make sure the QBI calculation has been deleted.‌ If it's been deleted, go back through your business entries.‌ As I mentioned before, TurboTax calculates the deduction automatically so it might just populate again. If this doesn't bring back the calculation, you might have to delete your business information and enter it again.  

How do I preview my TurboTax Online return before filing?

For more information about QBI, see the following TurboTax help article:

What is the Qualified Business Income (QBI) deduction?