Drivers are reportedly being fined for using a busy crossing after their accounts were “closed without their knowledge”.
Many Dartford Crossing users have automatic payments taken out of their accounts to cover the £2.50 fee to use the QEII bridge or the tunnel.
But people say they have received fines for several journeys spanning months after their accounts were shut without them knowing.
In August last year, there were problems with the Dart Charge website following a toll system update.
Drivers who used the tunnel and QEII Bridge to go between Essex and Kent said they had been left waiting on the toll service’s website for upwards of an hour trying to pay their fee.
At the time, National Highways asked those with accounts to log in and re-validate their payment cards.
However, it says the current issues do not relate to an IT system failure.
A spokesperson said: “When we changed providers for the Dart Charge Service at the end of July 2023, due to banking regulations all of our 1.7 million account holders had to re-validate their card details in order for us to continue taking payments for crossings made.
“All account holders were contacted in advance and prompted online, and to date 770,000 account holders have successfully updated their accounts.
“The Dartford Crossing has around 4.5 million crossings per month and the vast majority of crossings are paid without issue.
“A number of things can cause a Dart Charge account to close, including inactivity or invalid payment details.
“In these instances several notifications are sent to advise the customer of the account status and detail actions needed.
“However, we would encourage all account holders, particularly infrequent users to ensure their account details are up to date and there is a valid payment method on their account.
“All customers that receive a Penalty Charge Notice (PCN) can submit a challenge.
“All challenges are reviewed on an individual basis and decisions are made based on the circumstances and evidence provided.
“National Highways have taken steps to stop PCN’s being issued to customers due to issues faced during the transition to the new service and have been reducing or cancelling penalties where appropriate when an appeal is received from affected customers.”
