Gardai have hailed the new hi-tech licence-plate reader as the reason for greater road tax compliance, as related offences fall by 5,000.
The new Automatic Number Plate Recognition (ANPR) system was adopted in late 2008 and can read five licence plates in one second.
New figures released by An Garda Siochana involve offences related to road tax, including no tax, failure to display and failure to produce.
The gardai recorded 70,579 road tax offences in 2009 compared with 75,307 in 2008.
A garda spokesperson attributed the decline to improved technology and greater awareness on the part of the public.
"Obviously, the decline in offences is linked to greater compliance on the part of the general public," he said.
"There has been no reduction on the level of activity on our part, but with the technological improvements we have made, people now realise they can't afford to take the risk."
The figures have been viewed as progressive, but Green Party leader and Environment Minister John Gormley plans to tighten the laws further.
Mr Gormley, in a statement circulated with the Carbon Budget in December, said that there were important issues of motor-tax enforcement which need to be addressed.
He believes that there is a perception that it is permissible to use a vehicle in a public place if the tax is less than one month out of date.
This is not the case, and the Minister intends to end the tolerance to out-of-date tax.
The Minister also believes that the system of declaring vehicles off the road needs to be tightened significantly, and that compliant motor-tax payers are being disadvantaged by those who abuse the system.
These encouraging figures come days after details of a study were revealed stating that thousands of Irish motorists have stopped paying insurance.
The study from Friends First revealed that 25pc of those who have given up making insurance payments have ditched motor insurance, even though they are legally obliged to it.