Most British households receive energy bills that mix actual and estimated meter readings. When estimates are consistently off, the mistake often surfaces months later as a surprise “catch-up” bill — sometimes for hundreds or thousands of pounds. Ofgem's back-billing rules limit how far back a supplier can go.
The 12-month back-billing ban
Since 2018, Ofgem has banned domestic and microbusiness energy suppliers from seeking payment for gas or electricity used more than 12 months ago where the reason the customer wasn't billed correctly is the supplier's fault. See Ofgem's consumer guidance for the current rules.
The protection covers situations such as:
- Bills based on estimated reads when the supplier could have obtained an actual read
- A failure to bill at all for a long period
- Readings misrecorded after a meter swap
- Systems issues at the supplier that delayed accurate billing
When the rule doesn't apply
Back-billing protection does not apply where the delay was the customer's fault — for example, if the supplier was prevented from taking or receiving accurate meter readings, such as by obstructing meter access or tampering with the meter.
How to challenge a back-bill
- Ask for a detailed breakdown of the bill — actual and estimated reads, tariff rates, standing charges, and the period each charge covers.
- Identify the portion of the bill that relates to energy used more than 12 months ago. Send a written complaint stating that this portion falls under Ofgem's back-billing rules and that you are not liable.
- Keep paying for current usage while the dispute is live so the supplier cannot escalate to debt collection on undisputed charges.
- If the supplier can't resolve the complaint, ask for a “deadlock” letter, or wait 8 weeks from when you first complained, and then refer the dispute to the Energy Ombudsman. You must refer within 12 months of the deadlock letter. The Ombudsman's decision is binding on the supplier if you accept it.
Estimated vs. actual reads
If you think the catch-up bill is based on wildly wrong estimates, submit a meter read yourself and request the bill be recalculated. Smart meter data, if present, is especially useful — it gives half-hourly usage history that is hard to dispute.
Decision-support reminder: Fix My Bill flags potential issues with your energy bill for you to verify with your supplier. It is not a substitute for regulated advice and does not replace the Energy Ombudsman process.