An Post had its busiest December ever for parcel deliveries.
Three million parcels were delivered across the country over the Christmas period.
One million parcels were delivered in the week after Black Friday, which was a 35 percent increase on last year.
Garrett Bridgeman from An Post says clothes are the items that are returned the most.
"If you look at someone like Amazon or Smyths, customers are going online to buy something very specific that they know they're buying - an iPad or lightbulbs, something like that. They know exactly what they're getting, they have the certainty and they buy them," he said.
"What happens when you move into retail stores, say Arnotts, Brown Thomas or Zara, there's a higher element of returns there but they still have a physical store."