Energy Back-Billing: The 12-Month Rule
A surprise energy bill for gas or electricity used years ago? In most cases you only have to pay for the last 12 months.
It often starts with a new smart meter or a first proper reading in years. Then a bill arrives for hundreds or even thousands of pounds of energy used long ago. Before you pay, check whether the 12-month back-billing rule protects you.
What the Rule Says
Under Ofgem's rules, energy suppliers generally cannot charge you for gas or electricity used more than 12 months before the bill, if you were not billed correctly for it at the time. This covers homes and microbusinesses, and it applies when, for example:
- You were sent estimated bills that were too low
- You asked for an accurate bill and did not get one
- Your Direct Debit was set too low to cover what you used
When It Does Not Protect You
The rule does not help if you acted unreasonably, for example by blocking access to the meter, ignoring requests to pay or taking energy without paying. And any accurate bill for the last 12 months still has to be paid.
What to Do
- Check the dates. Look at which period the bill covers and when you were last billed accurately.
- Write to your supplier. Say you are relying on the back-billing rule and ask it to remove charges for energy used more than 12 months before the bill. Ask for any money taken in error to be refunded.
- Ask for time to pay for the part you do owe if you need it. Suppliers must help customers who are struggling.
- Go to the Energy Ombudsman if it is not sorted within 8 weeks, or sooner if you get a "deadlock" letter. It is free, and if you accept its decision the supplier must follow it.
Our guide energy back-bill: do I have to pay? has more detail and a template letter.
- What to do if you get a back bill (Ofgem, checked 18 October 2026)
- Our dispute resolution process (Energy Ombudsman, checked 18 October 2026)
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