Paymark figures show spending in the Otago region increased from $5.5 million on December 26, 2010, to $6.2 million this year - up by 12.3%.
The volume of electronic transactions also increased 8.2%, from 902,000 transactions last year to 976,000 transactions this year.
Southland spenders were not far behind with a 12.1% increase in spending and a 6.8% increase in transactions.
And the recent earthquakes in Christchurch seemed to have little impact on Boxing Day shoppers as spending increased 7.7% from last year to $10.7 million.
It was still above the nationwide average increase of 6.9%.
A total of just under $106 million was spent across the country.
Paymark head of sales and marketing Paul Whiston said although Boxing Day was a good day in terms of spending growth, December as a whole had been a good month for Kiwi retailers, with steady growth across most sectors and regions.
The steady growth may have been assisted by the wealth of big sales and heavy discounts across longer periods of time than consumers had seen in previous years, he said.
"Every year you're going to get a group of people who always come out in force for the Boxing Day sales and this year they certainly have.
"The growth is not as high as we saw a few years back, which suggests perhaps that we've found a level of stability in the wider Christmas shopping period.
"Growth of 6.9% across the country is a good positive end to the year for retailers," he said.
The Paymark network processes more than 75% of all electronic transactions in the New Zealand retail market.
