It's unclear how wide-spread the issue was, though by social media it's clear that Victoria, NSW and Queensland were affected.
Trolleys abandoned at the Caneland Woolworths registers.
Signs were put up at a number of Woolworths stores apologising for the problem.
"Shoppers have been told to leave groceries in baskets in the aisle", one customer from Brisbane wrote on Twitter.
In a statement, Woolworths said the outage was related to an IT systems update before registers came back online by about 4.30pm.
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Guardiola and his players will have the chance to celebrate properly on Sunday when they host Swansea in their next fixture. It was always a matter of when rather than if City would be champions after they led the way for most of the season.
Customers began to take to social media at quarter past 4pm to report that they were stuck in lines or told to leave the store while the issue is resolved.
A Daily Mercury reporter at the scene said services had just been restored and customers were once again flowing through the registers.
EARLIER: A NATIONAL technical outage has halted trading at Woolworths stores, causing chaos for shoppers as their trolleys bank up and stores are shut down.
Woolworths stores across the country have had to shut down registers and are unable to make sales.
An IT glitch has hit about half Woolworth's 995 supermarkets in Australia.