"Paymark transactions reached new highs before Christmas and over the month in general but figures also point to several pressures on merchants," he said.
"The annual growth rate was generally low and below the rate of the recent months that would have shaped retailer expectations. We also saw widespread discounting which appears to have accelerated the trend towards lower average transaction value. There continues to be growing use of scheme credit and debit cards which adds to the bank fees paid by merchants. And, to further pressure the bricks and mortar merchants, e-commerce growth has accelerated of late."
Hopper said there were also many sales, starting back on November 23 with Black Friday "and this may have pushed the average transaction value lower as well, although this is difficult to see in Paymark figures as only the total transaction value is recorded".
"There may have been more, or fewer, items than usual within each transaction as well."
The busiest day of 2018 recorded by Paymark before Christmas was December 20, with $296m worth of transactions processed.
What people spent their money on varied.
Toy retailers recorded 11.3 per cent higher spending through Paymark December to December. Also relatively strong were hardware and home decorating stores (6.1 per cent) and chemists (5.5 per cent). Spending growth on food and liquor was high relative to other merchants, including amongst supermarkets and liquor stores (3.9 per cent) and restaurants, bars and cafes (6.3 per cent), although both sectors experienced growth rates below those of recent months.
Spending declines occurred for accommodation merchants (-2.5 per cent), as well as amongst the above-mentioned electrical and electronic group of merchants (-19.9 per cent) and by clothing and footwear merchants (-4.7 per cent).