Hello Catrin,
I assume you mean October 2020. Since he has had an acknowledgement then I would not be overly concerned, things are taking a lot longer at the moment. However to put your minds to rest there is no harm in giving the DWP a ring see when the assessment might be.
Fortunately, any award he does eventually receive will be backdated to when the application was received.
Well done for stepping up to the plate and being willing to help!
Catherine
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
