Reg 8(1)(e) states re the CB extension that a person under 18 can be treated as a child (amongst other things) where "the person who is responsible for him has made a written request to the Board for the payment of child benefit during the extension period".

I can't find any mention as to the timing of the written request. Is it possible to make a written request at any time, such as after CB as stopped, to get it started up again?