Demand for new cars spiked in July
The volume of retail sales in Ireland rose by 12.6% between June and July, reflecting a spike in demand as 162 plates were introduced.
This has been a trend in every year since the new registration system was introduced in 2013.
If motor sales are excluded, there was a 0.5% fall in retail sales. This compares to an increase of 2.7% last year.
Motor sales increased by 12.5% - while furniture and lighting sales were 5.3% higher, according to the CSO.
The biggest decrease was in the footwear and textiles sector, which fell by 2.5%.
Meanwhile, new figures from the Bank of Ireland show a rebound in consumer sentiment following the Brexit vote.
Its Economic Pulse monitor rose by 2.5 points to 93.7 in August - clawing back a quarter of the dip in the previous month.
Loretta O’Sullivan, chief economist at the bank, said: "Although there has been a rise in sentiment, many consumers and businesses are still assessing the potential impact of Brexit.
"We will be closely monitoring the situation over the coming months."