The outage has also shut down entire stores.
Woolworths has not yet confirmed the exact cause of the problems.
"This type of incident should not occur and we apologise unreservedly to our customers and store teams for the inconvenience caused".
This story is developing.
UPDATE 5PM: FRUSTRATED customers took to social media after being forced to abandon their groceries at Woolworths registers due to a national technical fault.
Trolleys abandoned at the Caneland Woolworths registers.
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"Registers are offline so customers are standing in queues with baskets of food that they can't buy", she said.
The issue began affecting all registers across the country shortly after 4pm, leaving consumers with trolleys full of shopping but no way to pay. "We were all offered a box of chocolates".
Shoppers have taken to Facebook across Australia to complain about the outage, accusing the supermarket chain of "ruining dinner plans".
Others have been told to leave the stores. "Bad form. I'll stick to Aldi".
Woolworths has close to 1000 stores in Australia, though it's not known how many stores were affected.