If you have self-employment income from a 1099 MISC form that is reported on Schedule C, TurboTax will automatically calculate the Section 199a deduction for you. (If you have income from a K-1, you will need to upgrade to TurboTax Premier.) This deduction can be found on line 9 of your 1040 form.
After entering your self-employment income, TurboTax will ask a few questions that help determine if your business is eligible for the 199a deduction. These questions are whether the income was earned in the United States and whether the income was earned from a former employer. Otherwise, TurboTax will calculate the deduction for you as it is based on several factors, including your personal taxable income. For taxable income under the lowest threshold of taxable income of $157,000 single and $315,000 joint, the deduction is either 20% of your qualified business income (which is your business profit less self employment taxes, self employed health insurance premiums, etc) OR 20% of your taxable income less capital gains/dividends.
Here is more information on the deduction:
https://ttlc.intuit.com/replies/7019998
Here is how to preview your 1040 form in TurboTax Online:
https://ttlc.intuit.com/replies/3302322
