Thousands of gas customers could face higher bills and delays to switching while the industry’s central IT system is updated later this month.
All gas suppliers, including the Big Six, use the same computer network to share customer information and metering data.
This system will undergo a planned two-week period of maintenance from the 23rd of May to the 6th of June.
During this timeframe, anyone switching supplier may face delays in seeing changes to their tariff, meaning those switching to a cheaper deal during this time will likely miss out on potential savings until the update is complete.
Regulator Ofgem said consumers will face a maximum of a three day delay.