Just had my PIP review letter last one being 2018. If nothing has changed should I just leave out all previous information set to them, because on the form it says do not send any information you've sent us before.
I would have a look at the latest PIP guide on filling out the review form and what you should say. Even if nothing has changed the guide advises you to write something. You can find the information from page 129 benefitsandwork.co.uk/guides-for-claimants/pip. Many people submit supporting evidence that they have sent before because they are not trusting of the system. Others don't.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems