The UK back-billing rule, explained: when your supplier cannot recover old debt

What the back-billing rule says

Under Ofgem licence conditions SLC 21BA (domestic) and SLC 7A (microbusiness), since May 2018 a UK licensed energy supplier cannot recover charges for unbilled energy used more than 12 months ago if the supplier was at fault for not billing accurately. The rule applies to gas and electricity, and was designed to address a recurring pattern of customers receiving large catch-up bills years after the consumption.

The trigger is the date of accurate billing — not the date of the meter reading. If the supplier had a meter read but failed to bill accurately on it, the 12-month clock starts.

Who is covered

• Domestic customers: full coverage under SLC 21BA.
• Microbusiness customers: covered under SLC 7A. A microbusiness is defined as one with fewer than 10 employees (or full-time equivalents) and annual turnover (or balance sheet) below €2m, or consumes less than 100,000 kWh of electricity / 293,000 kWh of gas per year.
• Larger businesses: not covered by the licence-condition back-billing rule. However, common-law principles around limitation, set-off and contractual interpretation can still apply, and we routinely succeed in disputes for larger businesses on those grounds.

How to assess your case in five questions

1. Did the supplier issue you with an accurate bill within 12 months of the energy being used? (If yes, the rule does not apply to that period.)
2. Was the failure to bill the supplier's fault — for example, ignored meter reads, lost meter records, system errors? (If yes, the rule applies.)
3. Was the customer on supply throughout? (Tenant changes complicate this — supply continuity is checked separately.)
4. Have you ever told the supplier the bills looked wrong, in writing? (Strengthens your case.)
5. Did the supplier fail to act on a known problem — e.g. a flagged meter fault left unaddressed? (Strongest case.)

Filing a back-billing claim

The standard route:

1. Write to the supplier formally invoking the back-billing rule and citing the relevant SLC. Request a corrected bill capped at 12 months of energy.
2. Allow 8 weeks for resolution.
3. If unresolved, escalate to the Energy Ombudsman (free for domestic and microbusiness). The Ombudsman's decisions are binding on the supplier.
4. If the supplier still fails to comply, complain to Ofgem under SLC enforcement. Larger cases sometimes warrant solicitor-led escalation.

Common supplier responses (and how to handle them)

• "You should have submitted reads." Customers are not legally obliged to submit reads. The supplier is responsible for billing accuracy.
• "Our records show we sent you bills." Bills must be accurate. An estimated bill issued every quarter is not accurate billing if a real read was available.
• "This is a goodwill offer of 50%." Not enough — the rule, when it applies, caps recovery at 12 months, not a percentage. Goodwill offers can be a useful bargaining position but should not be accepted in lieu of the licence condition.

If you've received a back-bill that doesn't feel right, send us the timeline. The first call is free. More about our compliance casework.