Gas Back-Billing Rules: When an Old Charge May Not Be Payable

First, what counts as a back bill?

A back bill—sometimes called a catch-up bill—is a charge for gas or electricity that was used earlier but was not billed accurately at the time. It can follow a meter problem, a string of estimated readings, an account setup error or a supplier discovering that payments were too low.

The unnerving part is usually the size, not the arithmetic. Several billing periods can arrive as one demand. Before agreeing that the amount is due, check the dates it covers, the readings used and whether the supplier has already told you about those charges in an accurate bill or statement of account.

Ofgem’s rules do not wipe every old balance. They restrict how far back a supplier can newly charge in certain circumstances. An accurate bill that was sent at the time but left unpaid is a different situation.

How the 12-month rule works

Ofgem says you do not have to pay for energy used more than 12 months ago when you had not previously received an accurate bill for it, had not been told what you needed to pay through a statement of account, or your Direct Debit had been set too low to cover what was due.

The protection applies to domestic customers and microbusinesses. It is aimed at unbilled consumption, not at cancelling a valid debt that a supplier has already billed correctly. That distinction is why the paperwork matters: the date energy was used, the date it was first billed and the accuracy of the earlier account all need to be separated.

A supplier should recalculate a qualifying back bill so that consumption older than the protected 12-month period is removed. If money was taken for a charge that the rules cover, Ofgem says the supplier should refund it.

When the protection may not apply

The rule is not a route around paying for gas where the customer has acted unreasonably. Ofgem gives examples such as blocking access to the meter, ignoring requests for payment or stealing gas or electricity. A supplier that relies on an exception should be able to explain the behaviour it says prevented accurate billing.

Do not assume that any estimated bill is automatically protected either. A run of estimates can lead to a back bill, but the answer still depends on what was billed before, what information was available and what period the new charge covers. Equally, a low Direct Debit is only a monthly payment arrangement; it does not by itself prove that the underlying bills were wrong.

If the facts are disputed, ask the supplier to set out its calculation and its reason for saying the 12-month restriction does or does not apply. A clear written answer is far easier to check than a phone summary.

What to check before you contact the supplier

Put the revised bill next to the last year or two of statements. You are looking for a story that joins up: actual and estimated readings, tariff rates, dates, payments and any change of meter or account number. A photograph of the meter today will not prove an old reading, but it gives you a reliable starting point for the current account.

Use our gas-bill calculation guide if the supplier has converted meter units to kWh, and check the meter type if the scale looks implausible. Metric and imperial meters cannot be treated as though their displayed units are interchangeable.

• Mark the first newly billed date. Do not rely only on the issue date at the top of the bill.
• List actual and estimated readings. Note any sudden jump or meter exchange.
• Match payments to statements. A balance can be wrong even when every Direct Debit was collected.
• Keep correspondence. Save emails, chat transcripts, complaint numbers and the supplier’s calculations.
• State the outcome you want. Ask for the protected period to be removed, a corrected bill and an affordable plan for any valid remainder.

How to challenge a gas back bill

Contact the supplier promptly and say that you want the account reviewed under Ofgem’s back-billing rules. Give the dates and evidence rather than sending a general objection. Ask the supplier to pause collection activity on the disputed amount while it investigates, and continue paying undisputed current usage where you can.

If the supplier maintains the charge, make a formal complaint using the process on its website or bill. Ofgem advises customers to explain what happened, provide evidence such as statements and meter photographs, and say what would put it right.

A complaint can go to the Energy Ombudsman if the problem has not been fixed within eight weeks, or sooner if the supplier sends a deadlock letter saying it can do no more. The Ombudsman is independent of Ofgem and can review the evidence and require remedies.

If part of the bill is valid but unaffordable

A successful back-billing challenge may reduce a bill without removing all of it. Ask for the protected and payable periods to be shown separately. That makes it possible to check the correction instead of accepting a single replacement total.

Tell the supplier if the valid balance is more than you can pay at once. Ofgem’s consumer guidance says suppliers must work with customers to agree an affordable payment plan. Be realistic about current usage as well as the arrears; an arrangement that covers only the old balance can leave a new shortfall growing behind it.

This article covers Great Britain’s Ofgem rules. Northern Ireland has a separate regulator and complaints arrangements, so customers there should use local Utility Regulator and Consumer Council guidance.