Thames Water to pay over £11 million after business customers were incorrectly charged.


Is your business due a water bill rebate? 1,000’s of businesses are being overcharged £millions!


In April 2017 the Open Water Market was formed allowing non household customers to switch water supplier to obtain a better deal on their water supply contract.


Reducing their costs by anything between 6 and 18 percent dependant on the geographical locations of the customers sites.


During the transition period large quantities of customer billing data had fundamental errors. The wholesale water companies effectively transferred inaccurate water and waste water billing data into the core IT systems, this data underpins the water retail market.


The IT system known in the water industry as “The Central Market Operating System”  (CMOS) is the system that the water retail companies rely on for billing customers in the water retail market.


So if this market billing data is incorrect then the water retailer has to bill the customer in accordance with the data in the market, therefore if the charges are incorrect then the customer will be overcharged for years going forwards unless they have a water audit undertaken by experienced water consultants to audit the billing data and report back as to whether the bills are correct.

If the bills are not correct then an application has to be made to the relevant water retailer together with evidence and a properly formulated claim.


Some claims can be complex and very time consuming and can take 3 – 6 months or more to be approved by the water wholesaler and water retailer.

As there are £millions in terms of incorrect charging and the water retail companies bear the brunt of customer frustrations even though they are billing correctly as per the market data and the majority of the time it is no fault of their own.


Water Consultancy H2O Building Services reported refunds due to overcharging for a national Pool and Leisure club in excess of £300,000! a large proportion of the overcharges were due to the wholesaler Thames Water removing discounts which the customer had previously had prior to deregulation and incorrect tariff applications.


Graham Mann Senior Partner of H2O Building Services commented ” General overcharging and undercharging is not just an issue in the Thames Water area, it is a national problem.

We experienced overcharging on mass prior to market deregulation and now in the deregulated market its much worse, probably involving hundreds of millions across the country.

We are talking very serious money, businesses at this or at any time cannot afford to be overcharged.

A case in point is a national care home company with refunds and savings due to incorrect charging now stands at £700,000! this money is desperately needed to go into care.

Not only are the customers losing out, so are the water retail companies who are facing increased costs in processing claims and lost customers as they are being blamed for the incorrect charging when in fact it is the fault of their wholesalers.

As a consequence of an OFWAT investigation Thames Water to pay over £11 million after business customers were incorrectly charged


This is only the tip of the iceberg as many more investigations will no doubt be undertaken, meanwhile we carry on auditing customers bills, identifying incorrect charging and working with the water retail companies to correct the charges going forwards.