Shoppers bumped up spending last month, but how much of that was due to tax changes is not clear.
From October 1 GST rose from 12.5 percent to 15 percent while personal taxes fell.
Paymark, which processes 75 percent of electronic transactions in this country, today said that spending through the Paymark network grew 3.3 percent in October from a year earlier. That rate was nearly double that compared to the midyear months of May, June, July and August when it rose 1.8 percent.
The volume of transactions was up 4.9 percent last month from October 2009.
Paymark chief executive Simon Tong said a rise in the value of transactions had been expected, given the increase in GST.
But the combined volume and value figures indicated not only an increase in spending, but that people were buying more often, he said.
"One month's data is not enough to determine if the increase has come as a result of people having more money in their wallets, or simply because prices have gone up -- it would appear to be a bit of both at this stage."
Spending on big-ticket items declined, with furniture and appliance sectors down 6 percent and 14 percent respectively, year-on-year, reinforcing the belief that shoppers made the most of pre-GST rise sales, Mr Tong said.
The average value of electronic transactions in those two sectors fell 14 percent and 19 percent, respectively, suggesting October was characterised by heavy discounting or smaller purchases of lower-than-average price.
Sectors with strong growth during October were takeaways, which was up 10 percent, supermarkets up 9 percent, bars and clubs up 3 percent, and footwear up 8 percent.