Energy back-bill letter: the 12-month rule explained

What this kind of letter means

Your supplier has been guessing your usage for two years and now says you owe £847.12. Under UK back-billing rules they usually can't charge for energy used more than 12 months ago if the estimating was their fault.

This catch-up bill covers 26 months (September 2024 to October 2026). Ofgem's back-billing rules mean that if you weren't correctly billed through the supplier's fault, they can't charge for energy used more than 12 months before the bill. The exception is where you obstructed readings or didn't respond to requests for one. A reasonable portion of this bill may therefore be challengeable. Ask for a breakdown by period.

Things worth checking

• The bill covers 26 months. Back-billing rules usually limit catch-up bills to the last 12 months when the supplier is at fault.
• They plan to raise your Direct Debit automatically. You can ask them to agree a fair amount instead.
• Check the 'actual' reading on the bill matches your meter today.

Your options

• Ask for the 12-month limit. Write to the supplier citing back-billing rules and ask for a corrected bill.
• Agree a payment plan. For the amount you do owe, ask for it to be spread so your Direct Debit stays manageable.
• Complain to the Ombudsman. If they refuse after 8 weeks, the Energy Ombudsman is free to use.

If you ignore it

They'll raise your Direct Debit from £96 to £167 a month, which means you'd likely pay for energy they may not be allowed to charge for.

What usually decides this

Back-billing rules are on your side. If the estimating was the supplier's fault, they usually can't charge for energy used before November 2025.

The rules

• Energy suppliers can't bill households for energy used more than 12 months ago if you weren't billed correctly before and it wasn't your fault (for example, you didn't block meter readings).
  England, Wales, Scotland. Source: Ofgem: What to do if you get a back bill

Rules last checked 13 November 2026.

Words you might see

• Catch-up bill: A bill that corrects earlier estimated bills after a real meter reading.
• Back-billing: Charging for energy used in the past. In the UK this is usually limited to 12 months if it's the supplier's fault.

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