In Hillingdon, the specific formats required for documents to prove your address aren't clearly detailed in the available information. However, it's generally advisable to provide documents in a clear and legible format, preferably as copies of originals rather than handwritten notes.
If you need further clarification on the precise format for address proof, it may be helpful to check directly with the council or refer to the official guidance on submitting documents, such as submitting documents for housing benefit.