Most retailers however held off until Christmas Day, with other major stores including Briscoes, Rebel Sport, Kathmandu and Farmers all starting their online sales today, with physical stores operating tomorrow.
Consumers can expect anywhere from 10 to 70 per cent off the retail price, but generally only on certain items.
At West Auckland's Nido, which has recently gone into receivership, customers will find 50 per cent off the entire stock in store.
The sales come as latest figures show year on year spending is slightly down, but week on week, is surging.
As of 2pm Christmas Eve, Kiwi consumers had spent in excess of $166 million through the tills since midnight.
The busiest time of day at 12.30pm saw a peak of 204 transactions per second - a new record, topping the previous record of 188 transactions per second (the daily average is usually around 60 transactions per second).
Paymark had seen around 3 million transactions processed between midnight and 2pm Christmas Eve, and everything indicates the trends will continue with the Boxing Day sales.
Spending through Paymark on Boxing Day last year totalled $149m.
Consumer NZ CEO John Duffy said he had not heard of a Boxing Day sale starting as early as Christmas Eve.
"Traders need to be careful not to be misleading in the way they describe sales to prevent a breach of the Fair Trading Act."
Duffy said there were several things people could do to protect themselves while buying products online.
"Know who you are buying from, look for a '.co.nz' website if you are wanting to buy locally. It is also worth asking if the product is in stock and the expected delivery time before buying.
"Always pay with a credit and debit card as then if the products don't turn up as ordered, you can take it up with your bank."
Price and product comparison site PriceSpy said 13 per cent of products listed on the site on Boxing Day 2018 were found to have increased in price and the average discount offered was just 4 per cent.
