Energy back-billing: why suppliers can't bill you for more than 12 months

Your energy supplier just sent you a bill for £2,400 covering charges from three years ago. Their meter readings were wrong, they admit it, and now they want the lot. Here's the thing: in most cases, they can't bill you for more than 12 months of unbilled charges. It's called the back-billing rule, and it's been Ofgem's price for licensed suppliers since 2018.

What the law says

The Ofgem Back-billing Code, embedded in the standard supplier licence conditions, says a domestic energy supplier cannot recover charges for energy used more than 12 months ago if the customer was not properly informed of the charges through a bill or statement of account during that period.

The rule applies where the supplier is at fault - for example:

• The supplier failed to send accurate bills based on actual or accurate estimated readings
• The supplier didn't act on meter readings the customer provided
• The supplier delayed sending bills or correcting errors
• The supplier billed the wrong customer or address

It doesn't apply where the customer was at fault - for example, blocking access to the meter, providing false readings, or not paying bills they did receive. There's also a narrow set of exceptions (theft of energy, certain unmetered supply situations).

The 12 months runs back from the date the supplier first issued an accurate bill. If they billed you correctly today, they can charge for the last 12 months of usage. Anything before that, they have to swallow.

Step-by-step: how to challenge a back-bill

1. Don't pay yet. Once you pay, you've effectively accepted the charge. Many people pay by direct debit and only spot it later - reverse the DD if you can.
2. Demand the billing history. Ask the supplier for every bill issued on your account for the disputed period. Look for gaps, estimated reads, or bills that were never sent.
3. Identify the fault. Was it the supplier's failure to bill? Their failure to act on readings? Their error?
4. Quote the back-billing rule in your written complaint.
5. Use our energy bill complaint tool to structure the dispute.

Letter snippet

Dear [SUPPLIER],

>

Re: Account [NUMBER] - Back-billing complaint

>

On [DATE] I received a bill for £[AMOUNT] covering energy used between [START DATE] and [END DATE]. This includes charges for periods more than 12 months prior to your first accurate bill on this account.

>

Under the Ofgem back-billing principle, embedded in standard supplier licence conditions, you cannot recover charges for energy used more than 12 months ago where the customer was not properly informed of those charges in a timely manner. The records show:

>

- [No bills issued / Estimated bills only / Customer-provided readings ignored] between [DATES]

• The first accurate bill issued was on [DATE]

>

I require:

1. The bill to be reduced to cover only the most recent 12 months from the first accurate bill
2. Confirmation in writing within 14 days
3. A revised statement of account

>

If this is not resolved, I will refer the matter to the Energy Ombudsman after 8 weeks.

>

Yours faithfully,

[NAME] - Account [NUMBER]

If they say no

Suppliers regularly argue that estimated bills count as "informing" the customer. Estimates only count if they were reasonably accurate based on available data - wildly inaccurate estimates don't satisfy the rule.

• 8-week complaint window. If unresolved, refer to the Energy Ombudsman.
• Energy Ombudsman - free, binding on the supplier up to £10,000, 12-month referral window from the supplier's final response.
• For supplier-specific tips, see our British Gas company page and Octopus Energy company page.

FAQs

I switched supplier mid-period. Does the rule still apply?

Yes. The back-billing rule applies to the supplier that's now trying to bill you, regardless of whether you've moved on.

What if I genuinely owe the money?

The rule is about how recovery is permitted, not whether you used the energy. If the supplier failed to bill you properly, they lose the right to recover the older charges - even if you used the energy.

My bill was estimated for years and now they want a "true-up". Is that allowed?

Only for the most recent 12 months. Anything older that wasn't reflected in reasonably accurate bills is barred.

The supplier is in administration. Different rules?

The successor supplier (or SOLR - supplier of last resort) inherits the back-billing obligations.

Does this cover business accounts?

The 12-month back-billing principle was extended to micro-businesses in 2018. Larger business contracts have separate, contract-specific rules.

A multi-thousand-pound back-bill feels like a fait accompli. It usually isn't. The rule exists precisely because suppliers were leaving customers holding the bag for their billing errors.