West Australians are tipped to spend about $181 million today as department stores start the year's biggest sales.
Hordes of shoppers are expected from as early as 8am, when stores will offer discounts of up to 70 per cent.
The Australian National Retailers Association expects shoppers nationally to spend about $1.9 billion on Boxing Day, 5.5 per cent more than last year.
WA shoppers are expected to spend about $181 million, $153.4 million of it in "bricks and mortar" stores.
Chamber of Commerce and Industry WA communications manager Tim Bray said the post-Christmas rush would be a further boost for WA retailers, who were forecast to benefit from about $3.55 billion in sales this month.
"If this figure is reached, WA will have annual retail growth of 6.3 per cent, topping last year's 5.9 per cent," Mr Bray said.
David Jones regional manager Ben Webster said Perth stores were bracing for more sales shoppers this year because of the extended trading hours, which meant they could open from 8am to 6pm.
Last year, Perth stores opened from 11am to 5pm on Boxing Day.
The chain expects to sell 115,000 pairs of shoes, 500,000 towels and 30,000 handbags nationally today.
Women's clothing, some discounted 70 per cent, is tipped to be the most popular sales item.
Myer expects about 17 million customers at its post-Christmas sale nationally and more than 500,000 transactions today.
Myer's biggest discounts include up to 50 per cent off selected bed linen, towels and cookware.
Target public relations manager Mikaila Gaskell said many of its customers would also shop online.
Its stores would offer up to 50 per cent off some homewares today.