Energy suppliers process millions of bills a month. Their systems are automated, scaled, and fast. They're also wrong more often than anyone would like to admit.
Here are the errors we see most often, ranked by how much they typically cost.
1. Wrong unit rate vs contract
How common: Very. This is the single most frequent error we flag.
The supplier applies a rate that doesn't match what's in the signed contract. Sometimes it's a decimal point issue. Sometimes a rate change was applied on the wrong date. Sometimes the wrong tariff code was assigned entirely.
Typical overcharge: 2-8p/kWh. On a business using 100,000 kWh per year, that's £2,000-£8,000.
How to catch it: Compare the billed unit rate against the contracted rate. Simple in theory, tedious in practice when you're doing it across hundreds of bills.
2. VAT at the wrong rate
How common: More than you'd think, especially for smaller businesses.
Businesses that use less than 1,000 kWh of electricity per month (or 4,397 kWh of gas) qualify for the reduced VAT rate of 5% instead of the standard 20%. Many qualifying businesses are charged 20% because nobody flagged the eligibility.
Typical overcharge: 15% of the total bill value for qualifying businesses.
How to catch it: Check monthly consumption against the VAT threshold. If you're under it, you should be on 5%.
3. Climate Change Levy errors
How common: Occasional, but expensive when it happens.
Some organisations are exempt from CCL — charities, very small businesses, and those with Climate Change Agreements. If the exemption isn't properly registered with the supplier, you get charged anyway.
Typical overcharge: 0.775p/kWh (electricity) or 0.672p/kWh (gas) at current rates. Adds up fast on large consumption.
4. Estimated reads that never get corrected
How common: Very common, especially on meters without smart reading capability.
The supplier estimates your consumption for one billing period. Then another. Then another. The estimates drift away from reality, and nobody goes back to reconcile with an actual read.
Typical overcharge: Varies wildly. We've seen cases where estimated consumption was 40% higher than actual.
5. Standing charge mismatches
How common: Moderate.
The daily standing charge on the bill doesn't match the contract. It's a smaller number per day, but it compounds across a year.
Typical overcharge: £50-£200 per year per meter.
6. Overlapping or missing billing periods
How common: Occasional.
Two bills cover the same dates, or there's a gap between billing periods that either double-charges you or leaves consumption unaccounted for.
7. Duplicate bills
How common: Rare but not unheard of.
The exact same bill issued twice. Usually caught at payment stage, but not always — especially in organisations where different people handle procurement and accounts payable.
What to do about it
If you're checking bills manually, focus on the top three: unit rates vs contract, VAT rate, and CCL. These account for the vast majority of recoverable overcharges.
Or automate it. Edge checks every charge on every bill against the contract and flags anything that doesn't add up. Try it free.