If you have received an invoice from your energy supplier that relates to the use of gas and/or electricity from over a year ago, you may not have to pay this.  

If you have received a bill for a previous use of energy (such as gas or electricity) – this amounts to back-billing.  

Under the Ofgem back-billing rules (1), if you are an individual or a micro-entity, you cannot be charged for the gas or electricity that was used more than 12 months ago.  

Please note that the rules do not apply if you have acted so unreasonably that it has prevented accurate billing for the energy provider, e.g. blocking meter readings. 

If you have received a back-bill, inform your supplier of the Ofgem rules and your protection under these rules. Each energy supplier has their own terms and conditions that will include the Ofgem rules so you can refer them to their own standard conditions also. 

Make sure to enclose all evidence including the bills that have been back-billed as well as the bills you have paid. We would recommend sending this by both email and post to the relevant department, i.e. it is unlikely to get reviewed quickly if it is sent to a generic enquiries email address or office address.  

Should the energy supplier still make the demand for payment, you can bring a complaint to the Energy Ombudsman: https://www.ombudsman-services.org/complain-now  

You must provide your supplier with one last opportunity to rectify this by explaining you intend on bringing a complaint to the Ombudsman should this not be resolved promptly. This is since the Ombudsman requires evidence that you have already brought this complaint to the attention of your energy supplier before starting their complaints process. You can then attach this correspondence with the energy supplier and it will be investigated by the Ombudsman in the hope to resolve the issue.  

Should you have an issue with your energy provider, feel free to contact our team to assist you further: as@bailoransolicitors.com  

(1) https://www.ofgem.gov.uk/consumers/household-gas-and-electricity-guide/who-contact-if-its-difficult-paying-energy-bills/energy-back-billing-guide-your-rights