Signs have been put up at a number of Woolworths branches apologising for the problem, which has been described as a "system fault".
Social media posts indicate stores impacted locally include Walkerston and Caneland Central.
A woman named Rose, from Hoppers Crossing in Melbourne, told 3AW customers were offered lollies as they were asked to leave. Many have left full trolleys behind.
A national technical outage brought sales to a standstill at the busy Mackay city store this afternoon.
Sky News has reported that customers were told to leave and come back in an hour.
Camera Icon Woolworths Hilton in South Australia which has been forced to shut
A security guard was also stationed at the closed doors to turn shoppers away.
A Woolworths spokeswoman said the registers were coming back online now.
Around 4:30pm, customers began to report stores they were shopping in were closing and they had been told an IT issue affecting the cash registers was to blame. "We apologise for any inconvenience caused".
Supermarket giant Woolworths has suffered an IT outage this afternoon which affected registers at its stores nationwide.
Woolworths stores across the country have had to shut down registers and are unable to make sales.
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