To complain about a PIP assessor, you can start by writing a complaint letter to the DWP and when you are sending it you can use the address at the top of any letter you have about your Personal Independence Payment.  Another way you can complain about a PIP assessor is by phoning the DWP and if you choose this method, you need to make sure that you keep a record of when you call, who you speak to and the reference number for your complaint.