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Energy bills · UK guide

A shock energy “catch-up” bill? They can’t go back that far.

Last verified 20 Jun 2026 · Source Ofgem + Citizens Advice

If your supplier suddenly bills you for months — or years — of gas or electricity, Ofgem’s back-billing rule is on your side. They cannot charge you for energy used more than 12 months ago if you weren’t correctly billed for it. It’s an enforceable condition of every supplier’s licence. Here’s how it works and how to push back.

12 monthsMax they can back-bill
Every supplierLicence condition
£0Free to challenge
OmbudsmanFree after 8 weeks
How the rule works → Help with energy bills

The back-billing rule

Ofgem bans domestic and microbusiness energy suppliers from charging you for gas or electricity used more than 12 months ago if you hadn’t been correctly billed for it. You’re protected if any of these apply:

  • they never sent you an accurate bill for that energy (even if you asked);
  • they never told you the charges were due via a proper statement of account;
  • your Direct Debit was set too low to cover what you were actually using.

This is now an enforceable licence condition, so it applies whoever your supplier is. It covers the classic shock scenarios: a long run of estimated bills, a switch or smart-meter mix-up, or a supplier “catching up” after years of under-charging.

The one exception

The protection doesn’t apply if you actively prevented accurate meter readings — for example by blocking access to the meter or tampering with it. If the under-billing was the supplier’s fault or down to estimates, the 12-month limit stands.

What it does and doesn’t do

The ruleWhat it means for you
Caps how far back they can chargeCharges for energy used over 12 months ago (that you weren’t billed for) should be removed.
Doesn’t wipe recent usageYou usually still owe for genuine usage in the last 12 months — but you can spread it.
Right to a payment planYou can ask to repay what you owe over a reasonable, affordable period — ideally at least as long as the debt took to build up.
Protection from disconnectionIf you engage and agree a plan, you normally can’t be disconnected; extra protection applies if you’re vulnerable (Priority Services Register).

How to challenge a back bill

  1. Don’t pay it on the spot. Check which charges relate to energy used more than 12 months ago.
  2. Write to the supplier quoting Ofgem’s back-billing rule, and ask them to remove charges for usage over 12 months old that you weren’t correctly billed for. Keep a dated copy.
  3. Sort the rest fairly. For genuine recent usage, ask for an affordable payment plan, and check hardship grants and the Priority Services Register (see our energy bill help guide).
  4. Escalate if they refuse. Raise a formal complaint; if it isn’t resolved in 8 weeks (or you get a deadlock letter), take it free to the Energy Ombudsman — its decision is binding on the supplier.
Do this now
  1. Mark the dates on the bill — anything older than 12 months you weren’t billed for should come off.
  2. Email the supplier quoting the back-billing rule, and ask for a corrected bill + an affordable plan for the rest.
  3. Diary 8 weeks. No fair fix? Complain free to the Energy Ombudsman.

Free help: Citizens Advice consumer service 0808 223 1133 · the Energy Ombudsman. This is general information, not legal advice.

Source verification Primary sources: Ofgem (“What to do if you get a back bill” and the decision banning back-billing beyond 12 months) and Citizens Advice. Last verified 20 June 2026. Confidence: High — suppliers cannot bill domestic or microbusiness customers for energy used more than 12 months ago where the customer wasn’t correctly billed or informed, it is an enforceable licence condition applying to all suppliers, and the main exception is where the customer prevented accurate meter readings. The rule caps how far back charges can go but doesn’t wipe genuine recent usage, for which an affordable payment plan can be requested. SortedUK is independent — not a government service, an energy supplier or a law firm, and this is general information, not legal advice.

Energy back bills — common questions

My bills were estimated for two years — do I owe it all?

No. If you weren’t given accurate bills, the supplier can only charge for the last 12 months’ usage; anything older should be removed under the back-billing rule. Quote the rule in writing and ask for a corrected bill.

Does the rule apply to my business?

It applies to domestic customers and microbusinesses. Larger businesses aren’t covered by the back-billing rule, though other contract and fairness protections may still help.

They’re threatening to disconnect me — can they?

If you engage and agree an affordable plan, you normally can’t be disconnected, and there are stronger protections if you’re vulnerable (sign up to the Priority Services Register). Get free advice from Citizens Advice if they pressure you.

What if the supplier won’t budge?

Make a formal complaint, then after 8 weeks (or a deadlock letter) take it free to the Energy Ombudsman, whose decision binds the supplier. Keep all your correspondence.

A scary bill isn’t always a fair one.

Check the dates, quote the back-billing rule, and spread what you genuinely owe. Want help wording the email?

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