More than 14,000 cases of licence plate misreading were recorded on the country's busiest motorway over the past year and a half.
Transport Infrastructure Ireland (TII) said the most common reasons for a mistake on Dublin’s M50 were damaged or missing licence plates, deliberate tampering with plates by an owner, or an error in reading.
The average number of cases each month has been around 750 since the beginning of 2022.
However, TII said rates had been falling consistently since March of last year when almost 1,800 misreads were recorded to an average of around 340 per month so far this year.
The transport agency also said the number of mistakes was a tiny fraction of the journeys taken on the busy ring road with 87 million cars having passed through its automatic tolling system during the past year and a half.
Of that number, there were 14,280 misreads, or just 0.016% of the total, with that percentage falling over recent months.In cases of incorrect tolling, motorists are contacted by the M50 operator to say that they are entitled to a refund and that this will be automatically applied to their account.
Transport Infrastructure Ireland said a new operator for toll monitoring had begun work in August 2021, which had led to a temporary increase in the number of misreads.An information note said this was expected as there was normally a "period of optimisation and bedding in of new systems and processes".
"This is reflected by improvements over time in relation to misreads," they added.
TII said that the value of incorrect toll charges had been calculated at around €33,000 since the beginning of 2022 based on an average toll rate for all types of vehicles that use the M50.
They said when possible following a misread, attempts were made to see if the toll could be applied to the correct vehicle.
However, this was not always possible in cases of cloned registration numbers, "low confidence" in a reading, or where the owner of the car was deceased.
A spokesman for TII said: "For the month of July 2023, there were 4.9 million passages in total validated by the system with only 231 passages identified as misread, which is 0.0047% of all passages.
"There is continuous improvement which is evidenced by the decline of misreads over time. Unfortunately, it is not possible to completely eradicate all misreads. If there are any issues please contact … [your] customer service team."
