Water industry regulator Ofwat has had to issue an Information Notice to correct erroneous AMP6 data it used to calculate wholesale charges after the water companies flagged up the error.

In the draft determinations Ofwat set out companies’ allowed wholesale revenues for both water and wastewater services for the purposes of charging. The erroneous data was published in August in a technical appendix accompanying the draft determinations.

Since the draft determinations, a number of companies have informed Ofwat that the figures contained a calculation error. The error resulted in all figures in the table being 3% too small.

The regulator has now amended the calculations for the water companies’ final determinations.

Ofwat said that it may also update its Retail Price Index forecasts for final determinations to reflect the latest information available.

Click here for the revised figures on a company-by-company basis.