You do not usually need a formal diagnosis or a large bundle of documents to start a PIP claim. Useful evidence may include medical letters, care or treatment plans, prescription lists, test results, and statements from people who help you, alongside a diary showing how your condition affects daily living and mobility. Explain what you can and cannot do reliably, including whether activities take much longer, cause pain, or cannot be repeated. Send copies rather than original documents unless the Department for Work and Pensions asks otherwise, and check the latest guidance on GOV.UK.