CTC is being replaced by Universal Credit for most people –so no NEW claims unless:
If a child of 16 –then can claim up until 31/08 after their 16th birthday. If they are in approved education or training –can claim until 20th birthday.
From 27th January 2021 (the closing of the Severe Disability Premium ‘Gateway’), no new claims can be made for Child Tax Credit, on the basis of receiving the Severe Disability Premium (SDP).