As an Uber driver he's treated as an independent contractor and issued a Form 1099-MISC showing the amount earned.  To report his expenses -- including fuel -- click on the Business tab, then select I'll Choose What I Work On and you'll be taken to the page that says Let's Gather Your Business Info.  Next to Profit Or Loss From Business click on "start" or "update" and this will open up the business section where you'll see different headings like "Business Income" and, further down the page, "Business Expenses".  After entering his income in the Business Income section, you'll enter the fuel in Business Vehicle Expenses.  In this section, TurboTax will ask you about his car and the different vehicle expenses he has incurred.  You'll also get to select whether you want to take the actual expenses paid, or whether you prefer to take the standard mileage rate based on his business miles driven (the rate per mile for 2016 is $.54).  TurboTax will also calculate it both ways and tell you which is greater.