Cash was king for three hours on Thursday in Australia when ATMs and Eftpos went down across the country due to a Telstra outage.

Australian shoppers were left high and dry for three or more hours on Thursday when ATMs and some Eftpos terminals stopped working, due to a service outage with Telstra, the country's main telecommunication provider.

The nation's big four banks — Commonwealth Bank of Australia, Westpac Banking Corporation, Australia and New Zealand Banking Group and National Australia Bank — and many retailers, including Woolworths, Caltex Australia and Australian Post, were among those hit by the failure, leaving many shoppers unable to access cash or complete their payments at the checkout counter.

⚠️ALERT: Due to a telecommunications outage some merchants are unable to accept EFTPOS payments. We're sorry about this and will update you when services are back online. — ANZ Australia (@ANZ_AU) July 11, 2019

We are aware of an issue affecting some of our services. We apologise to our customers affected by this. Rest assured we are urgently looking into this and will have further updates soon. — CommBank (@CommBank) July 11, 2019

The outage began around 3 p.m. AEST on Thursday. Just before 6 p.m. AEST, Telstra confirmed the network was back. "Good news. Many of our services are starting to restore. We're sorry if this issue has messed up your night. We'll provide another update when we know more." the company said in a tweet.

Still, retailers lost money during the blackout period. Some restaurants had to let meals go unpaid and some petrol stations were also left hanging, when customers had no cash on them and were unable to get cash, because ATMs were also down, according to iTnews.

Things going well at Town Hall Woolies pic.twitter.com/Q00rlXtOID — Chris Dobespierre (@dobes) July 11, 2019

Just how much did retailers lose out on during the outage? Dominique Lamb, CEO at National Retailers Association, Lamb told the Sydney Morning Herald that in July 2018, AUS$837 million (US $585 million) was spent each day on retail purchases in the country.

"We know that basically, they were finding it very difficult to trade for the second half of that day which is ultimately going to have an impact ... we're predicting it's going to be up to $100 million [US$70 million]," she said.

The teleco is still investigating the cause of the outage but says early investigations point to "an unusually large volume of traffic" across networks in NSW Australia, according to the Herald.