Ofgem, the energy watchdog, has banned five companies from taking on any new customers until they fix the their data issues to let people with smart meters join them.
Daligas Limited, Enstroga Ltd, Entice Energy Supply Limited, Euston Energy Ltd (trading as Northumbria Energy) and Symbio Energy Limited have all had action taken against them after failing to make sure they are DCC (Data Communications Company) compliant.
Until they are, it means anyone joining with an existing smart meter could see it go "dumb", so Ofgem banned them from taking anyone on until they fix the issues.
"Suppliers are required to take all reasonable steps to roll out smart meters to all their domestic and small business customers by the end of 2020," Ofgem said.
"If these suppliers continue to fail to become DCC users in accordance with the final orders, Ofgem will consider further enforcement action, which could result in their licences being revoked."
All energy providers had to be DCC users from 25 November 2017 onwards to help with smart meter roll out.
Two months ago, nine suppliers were given final orders to join up, with a 31 March deadline, three of these (Ampower, Green Supplier, UK National Gas) have since managed it with another - Better Energy - no longer having any domestic customers.
That leaves five still not compliant as the deadline approached.
"Until these five suppliers are DCC users, customers with a DCC-connected smart meter who switch to any of the five suppliers will lose the functionality of their smart meter on switching," Ofgem said.
"This leaves the meters operating as traditional meters with customers needing to provide manual meter readings and unable to access the full benefits of smart meters.
"This causes consumer detriment and could undermine consumer confidence in the smart meter programme and the switching process."
