While the Avantax portal does not have an app, it is smartphone optimized. You can add to your home screen with the following instructions:
You can install the website as an app icon to your iPhone, so its easy for you to open: from there on, it will still be a website, but you would start it like an app. Here is how: open Avantax on your iPhone (in iOS Safari) and in the bottom bar click the icon that looks like an arrow coming out of a square (the "share" icon).Now click "Add to Home Screen" (this would be a gray square with a plus sign, like in the second row of options shown for sharing). Clcik Add on the next screen. It will look like an app but when you tap it, it will open the Avantax portal website.