I am sorry to hear your child has autism.
The IRS provides that if the child meets all the other criteria for a child dependent then age does not matter for earned income credit for a permanently and totally disabled child. This means that you will be able to claim your permanently and disabled child as a qualifying child and hence claim earned income tax credit no matter how old she gets if the other criteria are met.
However, the child tax credit is only allowed until your child turns 17 and after that you can claim other dependent credit for her.
What is a qualifying child for the Earned Income Credit (EIC) in 2020?
What is the Child Tax Credit?
