More than 200 thousand cars are on the roads with no valid NCT.
That figure is likely to rise due to a backlog in testing.
Tough new laws to be introduced next month will mean that motorists face a 60 euro on the spot fine and 3 penalty points for not having a current NCT cert.
Cars over 10 years need to pass the safety test every year, for cars between 4 and 10 years, its every 2 years.
Over 200 thouand cars currently have no valid cert as they wait for tests however some of the country's 47 NCT centres have a online waiting list of 3 months.
It comes as motorists are more likely to be stopped on the roads as garda checkpoints increase in the run up to Christmas.
