Separately, 'major discrepancies' have been discovered in the recorded numbers of breath tests
Thousands of drivers will have their penalties overturned after a serious mistake by An Garda Síochana.
The force has also admitted there is a huge discrepancy in their recorded breath test figures.
Between 2006 and 2016, there were 147,000 offences where a court summons was issued instead of a fine.
Of those, 96% had other offences that could have landed them in court - but almost 6,000 had no other offence and should have instead received a fixed charge notice.
All these cases will be appealed in court with the Gardaí not contesting the cases - meaning fines, possibly in the millions, will have to be repaid.
Superintendent Con O'Donoghue today apologised for the mistake, saying: "It represents a small proportion, but even at that we want to correct it and to make sure it never happens again".
Separately, the gardaí have discovered a massive discrepancy in their recorded number of breath tests.
Almost a million extra tests were recorded - with the gardaí admitting they do not know what caused the mistake.
Gardaí were recording the figures from memory instead of digitally.
Assistant Commissioner Michael Finn said they have changed their procedures to prevent more mistakes.
He said paper-based systems were "totally inadequate", and "we have to get new systems".
Gardaí say an internal investigation has been launched to establish how the mistakes occurred.
In a statement, the Policing Authority welcomed the force's public acknowledgement of the issues.
In relation to the breath test figures, the authority said: "This is not just an academic statistical matter, it is an ethical one. It raises serious questions of integrity for the Garda Síochána organisation and combined with previous issues regarding inflated activity levels, erodes confidence in the credibility of Garda data generally.
"In the view of the Authority, the scale of the discrepancy is further evidence of deep cultural problems within the Garda service – a culture in which such behaviour was possible."
The authority says that its concerns were raised with the Garda Commissioner this morning, and the issues "will continue to be pursued by the Authority as part of its oversight role".
Moyagh Murdock, chief executive of the Road Safety Authority, said: "While accepting both errors were due to a lack of adequate ‘checks and balances’ in the system, and that both issues have now been rectified to ensure they won’t be repeated, the fact remains that these developments are very worrying and our concern is that it damages the public’s faith in the ability of An Garda Síochána to effectively enforce life-saving road safety laws."