Keep your latest energy bill, previous bills, meter readings (including dated photos if possible), and your supplier account or customer reference number. It can also help to have payment records, your tariff details, and copies of emails or letters exchanged with the supplier. If you are applying for a scheme or asking for help, you may be asked for proof of identity, address, income or benefits, depending on the scheme. Ask your supplier what it needs, and check GOV.UK or Citizens Advice for current guidance if the issue is not resolved.