If your energy bill is wrong or backdated

Ofgem defines a back bill as a supplier asking for payment for energy you have already used but were not accurately charged for at the time — normally the result of a billing mistake or a problem with the meter. The back billing rules say the supplier cannot require you to pay for energy consumed more than 12 months in the past. That is the whole of the protection, and it is a licence obligation on the supplier rather than a favour it grants.

Ofgem sets out three circumstances in which the limit applies: where no accurate bill was previously issued, where no statement of account notifying you of the charges was provided, and where your direct debit was set too low to cover the actual charges. The third of those is the one people never expect, because a direct debit that the supplier itself calculated and never revised is a supplier failure, not a customer one, even though the money was quietly accruing on your own account.

The rules cover households and microbusinesses. Medium and large business customers are outside them, which is why a company that has grown past the microbusiness thresholds can receive a five-figure catch-up demand with no equivalent cap. If you are a business, establishing which category you fall into is the first question, not an afterthought.

It is important to be precise about what the rule does. It does not erase a bill that was correctly issued and simply not paid. Citizens Advice makes this point plainly: if the supplier did send you a bill within that year and you did not pay it, the supplier can still pursue that original bill. The protection is against being charged late, not against being charged at all.

Nor does it cancel the current period. The practical outcome of a successful back billing challenge is a reissued bill limited to the most recent 12 months of usage, with the older unbilled consumption written off. You should expect to pay the recent portion, and you should expect the supplier to offer terms if you cannot pay it at once — Ofgem requires suppliers to agree a payment plan you can afford, and to consider payment breaks, debt reviews and hardship funds.

Finally, the rule bites regardless of how sympathetic the supplier's explanation is. A migration to a new billing system, a meter that stopped communicating, a property that was mis-registered on the industry database — these are all reasons the supplier failed to bill accurately, and none of them is a reason the customer must pay for the failure.

Start with the account history rather than the disputed bill. Ask the supplier, in writing, for a full list of every bill issued on the account, with the date of issue, the meter readings used, and whether each reading was actual or estimated. That single document decides most back billing disputes, because Ofgem's test is about whether an accurate bill or statement of account was issued and when.

If no bill arrived at all for a long stretch, this is the cleanest case. Long silences usually follow a house move, a supplier transfer, a meter exchange or a change of billing system, and the customer is often the only person who noticed nothing was arriving. The silence itself is the evidence.

If bills did arrive but were estimated, look at how they were marked. Citizens Advice points out that an estimated bill will normally carry the word 'estimated' or an 'E' next to the reading. A run of estimates followed by a large correction when an actual reading is finally taken is the classic pattern, and where you were submitting readings that the supplier ignored, it is a strong case that no accurate bill was issued.

If you have a smart meter, check whether it was actually in smart mode. Ofgem notes that a meter which loses its communications link keeps measuring accurately but reverts to being read manually, and that where a supplier is not receiving automatic readings it must take all reasonable steps to get a reading from you at least once a year. Citizens Advice adds that the meter needs a connection to the wide area network, and that first-generation meters are being migrated remotely. A meter sitting in non-communicating mode for two years while the supplier estimated is a back billing case, not a smart meter case.

Check that the bill is for your meter. Every electricity supply has a meter point administration number and every gas supply a meter point reference number, and Citizens Advice recommends checking the number on the bill against the number registered to your address. Flats and converted properties produce a steady stream of bills for the neighbour's meter, and no amount of arguing about consumption will fix a bill for the wrong supply point.

Finally, separate a billing error from a measurement error. If the meter itself is over-recording, the bill may be arithmetically correct and still wrong. That is a different route, dealt with further down, and it is worth identifying early because the evidence and the timescales are not the same.

Photograph the meter today, with the date visible, before you do anything else. A dated photograph is the single most useful document in an energy dispute, because it fixes one point on the consumption curve that nobody can estimate away. Keep taking them monthly until the matter is closed.

Put the dispute in writing, even if you also ring. Citizens Advice advises gathering supporting evidence — photographs, copies of bills, notes from previous calls — and setting out what the problem is, when it started, and how the supplier can resolve it, with your account number and any case reference. If you do call, log the date, the time and the name of the person you spoke to.

Say the word 'complaint'. Ofgem's rules give suppliers eight weeks to resolve a reported problem, and that clock starts when you complain rather than when you first mention the issue, so a conversation that goes into a billing queue instead of a complaints queue can cost you two months. Ask for a complaint reference and keep it.

Be specific about the remedy you want. A useful formulation is: reissue the bill limited to the 12 months ending on the date of the corrected bill, in accordance with Ofgem's back billing rules; write off the unbilled consumption before that date; refund or credit anything already collected for the earlier period; and confirm in writing. Ofgem states that where a supplier has taken payment it should not have, it should refund it.

If the supplier says the rules do not apply, make it explain why in writing and identify which exception it is relying on. Vague assertions that the rules are 'not applicable in this case' are common and rarely survive contact with a specific question. If it says you obstructed metering, ask for the dates of the access attempts it says you refused.

Ask separately for time to pay the part you do owe. Ofgem requires suppliers to agree an affordable plan and to take your circumstances into account, and running the affordability conversation alongside the dispute stops the account escalating to collections while the argument is unresolved.

The back billing limit is not unconditional. Ofgem is explicit that you must pay for older usage if you have acted unreasonably, and it gives three examples: preventing accurate billing or blocking access to the meter, ignoring requests for payment, and stealing electricity or gas.

Meter access is the exception that arises most often, because it is the one that can happen through drift rather than intent. A meter in a locked cupboard, a landlord's box nobody has a key to, or a run of missed appointments over several years can all be characterised as preventing the supplier from billing accurately. Where you did offer access or did submit your own readings, say so and give the dates — a supplier's assertion that it could not read the meter sits badly next to a record of readings you supplied.

Ignoring requests for payment is the other common route out of the protection, and it is narrower than suppliers sometimes suggest. Citizens Advice's position is that where the supplier did send a bill within the year and it went unpaid, that bill remains collectable. That is not the same as saying that a single unpaid bill three years ago revives every unbilled period since; the question is what was actually billed, and when.

Energy theft removes the protection altogether and is a criminal matter in its own right. Ofgem describes tampering as costing consumers in Great Britain over £1.4 billion a year, notes the safety consequences — gas leaks, fires, electrocution — and says prosecutions can result in fines and imprisonment of up to five years. Tampering can be reported anonymously to Stay Energy Safe on 0800 023 2777. If you have moved into a property and discovered a tampered meter you had nothing to do with, report it immediately and in writing: the report is what separates you from the previous occupier.

Where a supplier relies on the exception, it is relying on a statement of fact about your conduct, and facts can be answered with records. Appointment letters, texts, submitted readings, emails and photographs of an accessible meter are the material that rebuts it. Keep them together in date order rather than describing them.

One point about tone. These disputes are decided on evidence and licence obligations, so there is no advantage in framing the complaint as an accusation of bad faith. State the rule, state the dates, state the remedy, and let the account history carry the argument.

A meter that over-records is a different problem from a bill that was issued late, and it has its own machinery. The starting signal, as Citizens Advice puts it, is paying more than usual or receiving a bill you were not expecting. A rough first check on a credit meter is to switch everything off at the sockets and watch whether the display keeps advancing.

The supplier has a defined duty once you report it. Citizens Advice sets out that it must check whether the meter is working properly, investigate any malfunction, and confirm what it has done in writing, all within five working days. Under Ofgem's Guaranteed Standards of Performance the supplier owes £40 for each of those steps it fails to complete, and a further £40 if the compensation itself is not paid within 10 working days. Prepayment meters have a tighter standard again: a response within three hours on a weekday, four at weekends, with £40 payable within 10 working days if that is missed.

Testing carries a risk worth knowing about before you ask. Citizens Advice says the initial test is free, but that where the meter is found to be working properly the supplier can charge for removing and reinstalling it — a figure it puts at around £200. That is a supplier charge rather than a regulated one, so confirm the amount with your supplier before agreeing to a removal test.

Behind the supplier's own process sits a statutory one. Under Schedule 7 to the Electricity Act 1989, meters must be of an approved pattern and construction and installed in an approved manner, certified meters must register within prescribed margins of error, and genuine disputes about accuracy are referred to appointed, impartial meter examiners who test the meter and report in writing. Section 17 of the Gas Act 1986 does the equivalent job for gas, requiring meters to be stamped by an appointed meter examiner and making it an offence to supply gas through an unstamped meter.

If the meter is found to be inaccurate, Citizens Advice says the supplier should refund what it owes you for the overcharging. The two rules then interact: a corrected bill issued after a metering fault is still a bill for previously unbilled energy, so the 12-month back billing limit applies to the correction in the same way it applies to any other billing error.

Do not let a meter test stall the billing complaint. Run them in parallel, keep the complaint reference live, and make clear in writing that the eight-week clock is running on the billing issue regardless of what the meter investigation concludes.

Not every wrong bill is a demand. A direct debit set above your actual consumption produces a credit balance, and Ofgem is unambiguous that this is your money: you can ask for a refund at any time on a live account, and the supplier must refund it promptly unless it has reasonable grounds not to. Suppliers typically review accounts annually against an actual reading and may refund automatically, but the annual review is not a reason to wait.

On a closed account the timescales are fixed by the Guaranteed Standards. Ofgem states that a final bill must be sent within six weeks of a switch and any credit balance refunded within 10 working days of that final bill, with £40 payable for each standard breached — a figure that rose from £30 for breaches occurring before 2 January 2025. The same standards regime covers switching failures: £40 for a switch that takes more than five working days, £40 for an erroneous transfer, and further £40 payments where the supplier misses the deadlines for putting it right.

Old accounts and old addresses are where credit balances go to die. Ofgem's advice for a closed account is to contact the previous supplier with the old account details; if you have moved, a forwarding address and a dated final reading are what turn a theoretical refund into a payment. Chase in writing and quote the standards.

Where the supplier has already collected money for a period the back billing rules protect, the remedy is a refund rather than a credit note, and you can ask for it to be paid out rather than held on the account. Ofgem's back bill guidance states that a supplier which has taken money it should not have should give it back.

There is a separate and much older backstop that occasionally matters. Section 5 of the Limitation Act 1980 provides that an action founded on simple contract cannot be brought after six years from the date the cause of action accrued. That is a limit on suing, it operates differently from Ofgem's licence rule, and it is far weaker in practice — the 12-month back billing limit will almost always be the more useful argument for a household or microbusiness. Treat limitation as a long-stop for genuinely ancient debts and take advice before relying on it.

Whichever direction the money is flowing, keep the account moving. An unpaid disputed balance can pick up collections activity, and Ofgem's rules on repaying debt through a prepayment meter — including the safeguards on installing one without permission, which require repeated contact attempts, welfare checks and exclusions for high-risk households — are protections you should not need to rely on if the dispute is properly logged as a complaint.

Ofgem requires suppliers and network operators to try to fix a reported problem within eight weeks, and tells consumers to record the date of first contact. If the problem is unresolved after eight weeks, if you receive a deadlock letter saying it cannot be resolved, or if you are dissatisfied with the response, you can take it to the Energy Ombudsman.

The Energy Ombudsman describes itself as a free and impartial service resolving disputes between consumers and suppliers, and it covers residential consumers and businesses in disputes with suppliers, brokers, network operators, heat networks, green deal providers and — since January 2026 — flexibility service providers. Ofgem states that suppliers and network operators must carry out the actions listed in the ombudsman's decision.

There is a deadline, and it catches people. Citizens Advice states that you must bring the complaint to the ombudsman within 12 months of receiving the supplier's decision. Where no decision has been given you may have longer, but there is no advantage in testing that.

What the ombudsman can do is practical rather than punitive. It can require a company to take a specific action — crediting an account, cancelling an account, changing a tariff — to apologise, to explain, and to make a financial award, and it can recommend changes to prevent recurrence. It says it cannot punish companies, dictate how they operate, or issue fines. Citizens Advice notes that once you accept the decision the complaint is closed and the outcome cannot be revisited, so read it before accepting.

Contact is by online form, phone or post. The Energy Ombudsman's number is 0330 440 1624, open Monday to Friday from 8am to 6pm and closed at weekends and on bank holidays, with post to Energy Ombudsman, P.O. Box 966, Warrington WA4 9DF.

Send a file, not a story. The account history you requested at the start, the dated meter photographs, the bills marked estimated, the complaint reference and the supplier's own written explanation of why it says the rules do not apply are the entire case. Ofgem also notes that Citizens Advice can refer complex or time-critical cases, and cases where personal circumstances prevent you dealing with the supplier, to its Extra Help Unit — worth asking about if the dispute is affecting supply or you are in a vulnerable situation.

Microbusinesses sit inside the protection. Ofgem's back billing guidance applies the 12-month limit to households and microbusinesses alike, and Ofgem's business guidance confirms that microbusinesses can escalate unresolved supplier disputes to the Energy Ombudsman, whereas medium and large businesses are left to civil court remedies. Microbusinesses also cannot be held to a rollover contract for more than 12 months.

That matters because business back bills often originate in contract mechanics rather than metering. A contract that ends without a new one agreed rolls onto out-of-contract rates, and premises taken over without a contract in place fall onto a deemed contract, both of which are typically expensive. If the supplier then failed to bill against them, you have a large sum accruing at a high rate — and the back billing limit applies to the unbilled part of it in exactly the same way.

In England and Wales, Citizens Advice runs the consumer service that handles energy complaints support, on 0808 223 1133, with a Welsh-language line on 0808 223 1144 and Relay UK access on 18001 then 0808 223 1133. It is open Monday to Friday, 9am to 5pm and closed on bank holidays. Advisers can explain the law and pass complaints to the supplier, though they cannot bring a complaint on your behalf.

In Scotland the same Ofgem rules apply, but the frontline advice service is different: Ofgem directs Scottish consumers to energyadvice.scot, run by Advice Direct Scotland, which handles supplier enquiries however complex, complaints procedures, billing problems, grants, heat networks and energy debt, on 0808 196 8660 from Monday to Friday, 9am to 5pm.

Northern Ireland is the real divergence. Electricity and gas there are regulated by the Utility Regulator, which covers the electricity, gas, water and sewerage industries in Northern Ireland and states that electricity and gas consumers are protected by minimum standards their supplier must follow. Its general enquiry number is 028 9031 1575. If your supply is in Northern Ireland, check the standards and complaint route that apply there before writing a letter built on Ofgem's rules.

The practical instruction is the same everywhere: identify the body that actually regulates your supply before you draft anything, then quote the rule that body has made. A complaint citing the correct obligation gets a substantive answer; one citing the wrong regulator gets a form reply and burns weeks of the escalation clock.