GST Credit for 17 year old

If the 17 year old is a parent of a child they qualify for GST

Seventeen seems a bit young but - if the daughter has any income of her own (small part-time job) - filing makes sense as may well get a refund if doesn't make enough to have to pay EI (earned less than $2,000 in the year).  Actually, once someone gets T-slips, filing is generally a good idea even if don't owe taxes as build up RRSP room.

When is the daughter's birthday?  If it's early in the year (think January - March) then she's already 18 at time of filing this year.  Filing her 2022 taxes will put her on the radar for becoming automatically eligible for her first GST payment in April, 2024 (or maybe even the January 2024 if she's a New Year's baby).  But she has to have filed a tax return.  From the CRA website:

If you have filed your tax return and you are entitled to the GST/HST credit, the CRA will issue your first payment on the payment date that comes after your 19th birthday".

Hope this helps.

Jo