I'm looking to use my unclaimed university credits from previous years in order to maximize my return so that I can start some investments. I want to properly claim them with the correct forms, how do I do so ?
You must claim your T2202A tuition amounts the year the T2202A was issued. In the same year, it must be used to offset any taxes you have payable. If there is any amount left, it will be carried forward throughout the years until it is used up. You can’t choose when to use your tuition, though you can transfer some to a spouse, parent or grandparent in the year you first claim it.
So to use your 2015, 2016, and 2017 T2202A tuition amounts, you must adjust the returns for those years, starting with 2015. Then you can add any amounts carried forward to your 2018 return, as well as your 2018 T2202A.
Here is how to claim tuition fees in TurboTax: https://turbotax.community.intuit.ca/replies/2647973
You can make changes after you have filed your tax return through the CRA or through ReFILE: https://turbotax.community.intuit.ca/replies/2647992