Masks, rising COVID-19 numbers and uncertainty over the Omicron variant have not deterred bargain hunters, who experts are tipping to spend more than $4 billion in stores and online.

The National Retail Association says it hasn't seen spending like this in 11 years, with pent-up demand from customers stuck in lockdown for much of the year.

Buying trends reflected how Australians were getting back to normal life, the association's CEO Dominique Lamb said.

Clothing, footwear, jewellery and personal items were popular as people move on from the comfortable loungewear bought for staying at home.

Yet household items were still trending heavily, she said, indicating many were still "preparing the nest" in case of another lockdown.

Department store chain David Jones expected to see more than one million customers in its stores nationwide on Boxing Day.

A spokesperson told AAP the retailer had started its online sales two days earlier on December 24 to help manage traffic in stores.

Swimwear, gadgets, lingerie and Lego sets were expected to be the most likely items to be snapped up on sale, the spokesperson said.

As shoppers make the most of the sales, consumer advocates are reminding them of their rights.

People are entitled to a repair when they buy or receive gifts that turn out to be faulty, Consumer Affairs Victoria says.

If something cannot be fixed then they are entitled to a refund or replacement, which applies even if the item was bought on sale or online.

While state governments consider whether to mandate a third vaccine dose, retailers are calling for more certainty.

Ms Lamb said business owners and consumers were confused about the advice on the Omicron variant and changing rules.

"Consistency is always best for us," she said.

"At the end of the day, we need to follow the science and we would hope this issue isn't politicised."

Retail staff have borne the brunt of customer anger with 56 per cent having suffered abuse during the pandemic, research by Sydney University and the Australian National University shows.

The retail workers union want shoppers to remember their manners as well as their masks.

"We know that shopping centres can be very busy and pressure can build as people seek a bargain, but it's no excuse to take out those frustrations on workers," SDA national secretary Gerard Dwyer said.

"Take extra care around the popular post-Christmas sales. Remember they often run for more than one day."

Australian Associated Press