I’m looking to apply for the DTC for my child, who recently turned 18. I’m in Ontario. Is there any option for a parent/caretaker to apply on their behalf? When I looked on my CRA account, I could only apply for a child under 18 but what if they’re not capable of doing the application themselves? Apply as a legal representative on their account? Send in a paper application? I realize that I should have done this MANY years ago but I didn’t. 
Any help would be appreciated.