Trolleys abandoned at the Caneland Woolworths registers.
Others have been told to leave the stores.
"It was really frustrating".
"The registers are now back online at all our stores", Woolworths tweeted just after 4.52pm.
"Registers are offline so customers are standing in queues with baskets of food that they can't buy", she said.
The supermarket giant has taken to Twitter to confirm the IT issue has since been resolved.
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"This type of incident should not occur and we apologise unreservedly to our customers and store teams for the inconvenience caused", Woolworths Group chief executive Brad Banducci said.
Seven News in Adelaide is reporting that some customers at a Woolworths store in Adelaide's west got their groceries for free after the nationwide outage.
Shortly after 4pm, the issue began affecting all registers across the country.
Registers temporarily shut down at a number of Woolworths stores across the nation due to a major technical outage this afternoon.
Registers have shut down with stores unable to make sales.
An IT glitch has hit about half Woolworth's 995 supermarkets in Australia.