While doing my 2016 taxes I realized I made an error on my 2015 indiana return that will probably result in a refund to me. How do I redo my 2015 Indiana return?

The 2015 online software is no longer available.

In order to amend your 2015 filing you have to purchase the 2015 Desktop Software here:  https://turbotax.intuit.com/personal-taxes/past-years-products

Once you are in the software you type "Amend" in the "Search a topic" box at the top of the screen and select "Find"

TurboTax will guide you through the process.