If you are applying for a non-evidenced extension, you do not need to provide evidence.
If you are applying for an evidenced extension, this request will not be considered unless evidence is given when making your application. You should provide as much supporting evidence as possible. Independent evidence should normally be provided via a verifiable document, from an appropriate third party. The document should give details of your circumstances, the dates and/or duration and, where possible, its impact on your studies.