As keen shoppers rush early to malls and stalls, retailers are expecting overall Boxing Day spending to top $1.8 billion.
The Australian National Retailers Association (ANRA) predicts Victorians will spend the most at $588 million, closely followed by NSW on $511 million.
Victoria has unrestricted trading across the state, but NSW has public holiday shopping restrictions outside tourist precincts.
Big spending is expected to continue across Australia on Thursday, with a predicted spend of $1.2 billion.
Spending for the first week of the sales is predicted to top $5.7 billion, with NSW spending the most at $1.7 billion followed by Victoria on $1.4 billion.
Clothing, homewares and electronics will be the most popular items bought, the ANRA says.