Tens of thousands of shoppers across the country have headed to malls to cash in on deals proving too irresistible to miss.

People and traffic have queued for their chance to grab a bargain that will see them save as much as 70 percent at some of New Zealand's biggest stores.

In Auckland the lure of saving money is causing a headache for motorists on Auckland's Southern Motorway and Mt Wellington Highway as shoppers heading to Sylvia Park clog main roads.

The NZ Transport Agency is warning people to avoid the area altogether or expect delays if they are heading to the mall.

Traffic is also banked up in Hamilton with people searching for car parks at The Base where motorists report mayhem on the roads from early this morning.

Waikato police said traffic was starting to back up down Te Rapa and asked motorists to be patient on the roads this morning if they were heading out to get a bargain.

In Auckland long lines have formed outside stores.

Shopkeepers keen to cash in on the busiest retail day of the year are slashing prices on some big ticket items across major brands and all major stores are offering tantalising deals.

Last year Kiwis spent more than ever before on Boxing Day, spending a record $152.7 million through Paymark, according to the company's figures.

Pre-Christmas spending has risen again this year, with expectations the holiday period could be another record year for retailers.

On Thursday Kiwis spent $282.4 million in a single day, with 178 transactions per second during the peak which occurred just after noon - a new record.

And as the shops fill for the Boxing Day sales there's confidence online sales won't kill off the annual tradition of heading to stores and malls to hunt bargains.

Amazon Australia is among the web retailers trying to entice buyers with online Boxing Day price slashing.

Retail New Zealand spokesman Greg Harford said although it would be a busy day local retailers also needed to be online to survive.

A survey shows one in 10 New Zealanders have put off Christmas shopping until today to snag a bargain.