The company's executive general manager of parcels, Bob Black, said more than 2 million parcels were expected to be delivered, making it the biggest delivery day in the nation's history.

More posties and delivery drivers have been called to handle the load, while an additional 1500 people have been brought on to help staff in processing facilities.

Mr Black said Australia Post had experienced unprecedented early volumes of parcels since October, with more than 1 million processed every day as consumers took advantage of pre-Christmas sales.

Because many retailers had offered pre-Christmas discounts, such as on Black Friday, a shopping day recognised in the US and now widely offered by online retailers, there has been a corresponding boom in internet shopping, he said.

"We're finding close to 30 per cent of all online purchases occur in the three months leading up to Christmas, and that's on the back of a 15.9 per cent growth in online shopping this year."

Mr Black said clothing and toys were the most popular buys.

Australia Post shops will be open longer to help customers collect their parcels after work hours.

Evening and weekend deliveries have also begun.