I am in the process of applying for PIP and trying to get together my supporting evidence before the form to fill in comes.
I have OH reports from my former employer and a medical report from my GP but wondered if I send in the confirmation of my receipt of Universal Credit (low Capability for Work element) in with it would that support my application?
It is up to you what evidence you send in, but you want to make sure that whatever you send in is relevant. Unless the receipt has some relevant information on it, pertaining to the PIP criteria then you don't need to include it. PIP isn't about your ability to work, it's about how you manage your daily living.
I would have a good look at the pip guide when you're completing your form