How Our Bureau Team Uncovered And Challenged Unexpected Energy Overcharges
Changes to energy charges can be difficult to navigate, particularly when it isn't clear how a supplier has calculated and passed them through. Businesses need to know that what they're being charged is right.
That is exactly what our Energy Bureau team uncovered following changes to Transmission Network Use of System (TUoS) charges in April 2026.
Here, our Head of Bureau, Lindsay Williams, explains how our team identified unexpected changes on client invoices, challenged the supplier's calculations and prevented more than £32,000 in annual overcharges across four clients.
What are TUoS charges?
Transmission Network Use of System, or TUoS, charges contribute towards the cost of operating and maintaining Britain's high-voltage electricity transmission network. They form part of the non-commodity costs that make up a business's overall electricity bill and, from April 2026, TUoS Standing Charges increased significantly.
On average, the standing charges increased by around 60%. The scale of the increase meant that contracts which had previously been fully fixed were opened up to prevent suppliers having to absorb the additional cost.
Most suppliers dealt with the change relatively transparently. They either increased the existing standing charge or added a separate TUoS Standing Charge line to invoices. However, our Bureau team noticed that one supplier had taken a different approach.
Taking a closer look
As part of our usual invoice validation process, we reviewed clients' April invoices and noticed that both the unit rates and standing charges no longer matched the rates in their contracts.
So, we queried the discrepancies with the supplier. The supplier confirmed that it had uplifted both the unit rates and standing charges to accommodate the increase in TUoS Standing Charges. The increases also varied according to each customer's estimated annual consumption”.
While an increase was expected, the way it had been applied made it difficult to establish whether the additional amounts being charged were reasonable. We decided to look at the figures in more detail.
Putting figures to the test
Our Bureau team built a detailed calculation using each customer's contracted standing charge, unit rates and estimated annual consumption to establish their expected annual cost. We then repeated the exercise using the supplier's new rates.
The difference was significant. The increases being applied were far higher than we expected to see as a result of the TUoS change.
We asked the supplier to provide its methodology and calculations so that we could understand how it had arrived at the new figures. When we tested the methodology, the numbers simply didn't add up.
Rather than accepting the explanation, we continued to challenge it.
Challenging the charging methodology
We asked the supplier to change its approach and apply the additional TUoS cost through the standing charge only. This reflected the approach being used by most other suppliers and, importantly, created a much clearer charging structure that could be checked and challenged.
The supplier agreed and provided a new set of figures. When we checked them, however, we identified further overcharges. We challenged these again and ultimately the supplier agreed to use the figures calculated by our Bureau team.
As a result of our intervention, invoices covering April to June 2026 are being credited and rebilled using the agreed methodology, with the revised approach also being used for future invoices. Had the original methodology remained in place, the four affected clients would have continued paying the higher rates.
Across those four businesses, we estimate the original methodology would have resulted in additional annual costs of £32,519.91. This case demonstrates why businesses shouldn't assume that every charge on an energy invoice is correct.
Businesses shouldn't assume that every charge on an energy invoice is correct simply because it comes from their supplier. Changes to network charges, regulation and the wider energy cost stack can make business energy bills increasingly difficult to understand. Even when an increase itself is legitimate, it is important to understand how that increase has been calculated and passed through.
More than checking an invoice
Our Energy Bureau service is designed to give clients another layer of scrutiny over their energy costs. We validate invoices against contract terms, monitor consumption and charges, query discrepancies and deal directly with suppliers when something isn't right.
In this case, spotting a difference between the contracted and invoiced rates was only the beginning. The real value came from understanding what should have been charged, doing the calculations independently and continuing to challenge the supplier until the issue was resolved.
For our clients, it means greater confidence that the energy costs coming into their business are being properly checked, rather than simply processed and paid.
If you've noticed unexpected changes to your electricity invoices since April 2026, or you're unsure how your supplier has passed through the changes to TUoS charges, speak to our Energy Bureau team. We can review your invoices, explain what you're paying and check whether the figures stack up.