British Gas tariff — slab structure and rate components
British Gas gas tariff is approved by Office of Gas and Electricity Markets and is published in Ofgem's tariff orders. This page explains the structure — slabs, fixed charge, fuel pass-through, and statutory levies — and points you to the authoritative source for current per-unit rates.
Tariff structure — how ${provider.name} bills are calculated
British Gas bills are calculated by applying the regulator-notified per-unit rate to your units consumed, then adding fixed charges, fuel pass-through, and statutory levies. The order of operations matters because some lines are percentages of others.
Residential tariff in United Kingdom is typically slabbed — a graduated rate where the first block of units is priced lower than the next. The exact slab boundaries are notified by Ofgem in periodic tariff orders. For British Gas, the current slab table is published at https://www.ofgem.gov.uk/.
Commercial and industrial tariffs are typically non-telescopic, meaning all units in a cycle are priced at the slab the monthly total lands in. Be aware of this when crossing slab thresholds for a small business.
Fixed charge
The fixed charge is a flat monthly amount tied to your sanctioned load. Paid regardless of consumption. It funds the meter, the service-line maintenance, and the operator's customer-service infrastructure.
Reducing your sanctioned load (where appropriate) lowers the fixed charge. If you are paying for a 5 kW sanctioned load but actually use 2 kW, apply for a load reduction at British Gas's customer service — the fixed charge drops proportionally.
Fuel pass-through
Gas bills typically include a similar pass-through line where input-cost fluctuations are billed monthly.
The pass-through is approved by Ofgem on a regular schedule (monthly or quarterly). The figure on your bill is the pass-through for a past period, not the current consumption month. Pass-through can be positive or negative.
Pass-through is the single most volatile line on most gas bills. A spike in fuel costs in one quarter can move the total bill by 10-25% in either direction in the following quarter without any change in your consumption.
Statutory levies — taxes, duties, and surcharges
United Kingdom bills include national and provincial taxes layered on top of the energy charge. The exact composition varies, but typically includes a general sales tax (VAT/GST), an electricity duty (provincial or state), and one or more financing surcharges that fund the country's power sector debt.
Statutory levies are percentages applied to base amounts; understanding the base of each percentage is key to predicting how a change in consumption translates into a change in the total bill. The bill explicitly shows the rate of each levy and the base it is calculated on.
Some statutory levies have an opt-out for compliant taxpayers (e.g., income tax withholding for tax-return filers). If United Kingdom offers such an opt-out, check with the relevant tax authority for the application steps.
Verifying your bill against the published tariff
On every British Gas bill you can cross-check the math against the regulator's published tariff in three steps. First, multiply your units consumed by the slab-applicable per-unit rate to verify the energy charge. Second, add the fixed charge for your load category. Third, add the pass-through line (if any) and apply the statutory levies as percentages.
If the bill does not match the formula, the most common causes are: a slab boundary you didn't notice, a tariff revision that took effect mid-cycle (the bill prorates between the old and new rate), or an arrears line from a previous unpaid bill.
If after checking all three you still cannot reconcile the bill to the formula, file a complaint at British Gas customer service (0333 202 9802). The operator's customer service can pull up your consumption data and walk through the calculation with you.