A fifth of all motoring offences result in the offender paying no fine or incurring no penalty points on their licence.
The report from the Comptroller & Auditor General deals with wasteful spending and lost income at all levels of government.
But one of its key findings is that the system for dealing with motoring offences has major shortcomings.
It finds that one in five offences end up resulting in no fine, penalty points OR a court appearance.
That's as a result of the tickets being lost or spoilt, the summons being issued to a company - which cannot take any penalty points - or a summons simply not being delivered.
In a number of cases the penalty points notice was issued so late that a refusal to pay the fine resulted in the case being statute barred - where it was legally too late to pursue it any further.
The report also details a small number of the reasons for which a notice was struck out and the offence terminated.
One speeding motorist said they were late for a swimming lesson, while another said they weren't concentrating - because they were preoccupied by the news that a cow on their farm was dying.
