You won't be able to install TurboTax 2017 on OS X 10.9.5 (Mavericks) or 10.10.5 (Yosemite). It can only install and run on 10.11 (El Capitan) or higher. More info
You can still use TurboTax 2016 on 10.9.5 and 10.10.5, but it might not run as well as it would on El Capitan. Additionally, your computer may not be adequately protected from the latest security threats. However, we'll continue to support TurboTax 2016 installed on these older operating systems, unless the problem is solely attributable to the operating system itself.