An investigation has been launched to “prevent such an error in the future”.
Operators of the “barrier-free” tolling system, eFlow, have announce that over 2,600 of their customers were overcharged last month.
An email issued to the affected customers on 19 July said that the company “unintentionally processed” the customer’s monthly invoice amount twice for the month of June.
They have since released a statement further explaining the situation.
It reads: “eFlow can confirm that there was a system processing error that affected 2,672 customers, which equates to 0.29% of our customers.
“All customers impacted by this error were contacted by eFlow to express our sincere regret at this system failure and advised of their refund options.
“This was an isolated incident and eFlow is currently undertaking an internal investigation to provide assurances to our customers and to prevent such an error in the future.
“We would again like to apologise to our customers that were affected by this.”
eFlow have said that a full refund will be made available to those affected, or they can use the funds that were taken again as credit in the future.
Those charged twice for this month’s toll tag bill should contact 1890 50 10 50 for more information.