What Ofgem’s billing review actually found
Suppliers have wiped more than £172 million off bills for almost a million households, and it happened under a rule most people have never heard of. Ofgem’s billing review, its first detailed look at how domestic billing actually works in practice, was published in July 2026, and the numbers are the clearest evidence yet that back billing mistakes are common.
The rule behind it is straightforward. If a supplier fails to bill you correctly and tries to charge you for energy used more than 12 months ago, and the error was genuinely their fault, they have to write off the older portion rather than pass it on to you.
Who got caught out, and by how much?
Ofgem’s billing review covered the big names, including British Gas, EDF, E.ON Next, Octopus Energy, OVO and Scottish Power, and found real differences in how well each one handles the rule. Some suppliers resolved back billing cases in around two months on average. Others took close to ten.
That gap matters more than it sounds. A slow supplier isn’t just annoying, it often means a customer sits for months not knowing whether a shock bill will actually be reduced, which is exactly the kind of uncertainty the 12 month rule was meant to prevent.
Most customers, to be fair, do get regular and broadly accurate bills. Ofgem’s billing review found the bulk of billing works as it should, with the back billing failures concentrated in a smaller pool of accounts, mostly credit meter customers where a reading was missed or an account error went uncorrected for a long stretch.
That’s a genuinely important distinction. This isn’t a story about every household getting overcharged, it’s about a specific, identifiable group who ran into a specific failure, and roughly a million of them got money back as a result once Ofgem’s billing review put a number on it.
Ofgem’s billing review in a nutshell
- £172 million written off for almost a million households under back billing rules.
- First detailed Ofgem assessment of how suppliers actually apply the rule.
- Resolution times ranged from around two months to close to ten, by supplier.
- Weak record keeping was flagged as a risk to consistent protection.
Why did Ofgem look into this now?
Because the back billing rule only works if suppliers actually apply it properly, and record keeping across the industry turned out to be patchy. Ofgem’s billing review found that poor internal records could mean the same situation gets handled differently depending on which supplier you happen to be with.
Roo’s take: a rule that only sometimes gets followed isn’t really a rule, it’s a lottery. Ofgem checking who’s actually playing fair is overdue, not surprising.
Could you be one of the million?
Possibly, if you’ve ever had a bill land that covered energy from over a year ago. The clue is usually a sudden, large charge after a long period of low or estimated bills, often following a switch, a meter issue, or an account error that went unnoticed.
If that sounds familiar and you’re still being asked to pay the older portion, you don’t need to wait for your supplier to notice. Raise it directly, quote the back billing rule, and escalate to the Energy Ombudsman if you don’t get a straight answer within eight weeks.
What should you actually do about it?
Check any bill that arrives with charges going back further than 12 months before you pay it. Ofgem’s billing review makes clear this isn’t a rare edge case, it’s happening at scale, and suppliers don’t always apply the writ off automatically without being asked.
Keep meter readings and old bills where you can find them. They’re the easiest way to prove exactly when a charge should and shouldn’t apply if a dispute ever needs evidence behind it.
If you’re on the Priority Services Register, this is doubly worth flagging to your supplier directly, since extra support is meant to apply here too. Prepayment customers should take particular note. Ofgem’s billing review flagged that record keeping gaps hit some payment types harder than others, and a household on a prepayment meter has less room to absorb a large backdated charge than one paying by direct debit with some slack in the account.
If your supplier resists applying the rule even after you’ve raised it clearly, put the request in writing and keep a copy. A written record makes it far easier to escalate to the Energy Ombudsman later if the conversation stalls, and it removes any ambiguity about what you actually asked for and when.
Frequently asked questions about Ofgem’s billing review
- What is the back billing rule Ofgem’s review looked at?
- Suppliers can’t charge you for energy used more than 12 months ago if the billing error causing the delay was their fault, not yours.
- How much did Ofgem’s billing review find had been written off?
- More than £172 million across almost a million households, based on Ofgem’s first detailed assessment of domestic billing practice.
- Does the rule apply if the late bill is my own fault?
- Generally no. The 12 month protection applies when the supplier’s error caused the delay, not when a customer failed to provide meter readings themselves.
- Which suppliers were covered by Ofgem’s billing review?
- The review covered major suppliers including British Gas, EDF, E.ON Next, Octopus Energy, OVO and Scottish Power.
- What should I do if I get an old, unexpected bill?
- Check the dates involved, query anything over 12 months old directly with your supplier, and escalate to the Energy Ombudsman if it isn’t resolved.
Ofgem’s billing review doesn’t change the back billing rule itself, it just proves suppliers don’t always follow it consistently, and that a written record on your side is worth having. If a bill lands that looks wrong, that’s reason enough to question it rather than assume it must be correct. For the rule in full, see our guide on energy back billing explained, and if a supplier isn’t budging, our piece on making an energy ombudsman complaint covers what happens next.
