If you have been assessed and you have received a copy of the assessment report (PA4), but you haven't received a copy of the assessment report - you can write to the decision-maker and put forward what you don't agree with. You won't get a reply to this letter and you won't know whether it gets put on the system in time for the decision maker to see it. (You don't know who the decision-maker is so you just have to address it to that title). I can't tell you whether writing this letter is successful or not.
If the PA4 is peppered with lots of errors, you could put in a formal complaint to the assessment services that carried out the assessment and inform the DWP that you have done this and the reasons why.
Otherwise you can wait until you have the decision letter and put in for a Mandatory Reconsideration. Only 27% are currently successful - and I mention that only so you know, not as a deterrent for putting one in. The 27% who win obviously consider it worth it.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems
