Where can I enter my business car mileage for self-employment please?

For business related automotive expenses, you can use the “T2125 Statement of Business or Professional Activities” form. To fill this in using TurboTax Online, click on the “Find” icon in the blue menu and search for “self”. Select “Self-Employment” and then click the “Go” button. The EasyStep interview will eventually bring you to the “Motor Vehicle Expenses Summary” where you can add you mileage and other related information.