From Tuesday, people can use an app created by Australia Post as proof of age at four Civic venues.

The app - called Digital iD - is a digitised version of Australia Post's Keypass card, a proof-of-age card used across Australia for the last 25 years.

Staff at a venue match the customer's face to their photo on their Digital iD profile, the same as they would if they produced a physical licence, or scan a QR code to verify the customer's identity.

Four venues - Shorty’s, Mr Wolf Nightclub, Kokomos and Akiba Restaurant and Bar - are taking part in the three-month trial, which has the backing of the ACT government.

Digital iD's general manager Cameron Gough said increasingly people were using their smartphones to pay for items and this app was an extension of that.

“We’re seeing people increasingly want to leave their wallets at home as loyalty cards, payments and more shift across to the convenience of a smartphone. Mobile payments has accelerated this shift in the past 12 months but ID documents remain a challenge," Mr Gough said.

Mr Gough said Australia Post had been involved in identity verification for many years,  providing the service to "about a quarter of the population every year" through passports, driver licence renewals in some states, and working with children checks.

He said the data was encrypted, so no Australia Post employee could access a user's personal information.

The app also used a separate pin, face ID or touch ID so the identity documents could not be accessed if the phone was stolen.

A screenshot of someone else's app won't fool bar staff either.

If the phone is shaken while the app is open it displays an animation, proving the ID is genuine.

Licenced venues in Victoria have previously trialled the app with success.

Kokomo's and Akiba co-owner Mike Harrington said these venues opted into the trial because they wanted to be at the forefront of the industry.

While less than 1 per cent of his customers pay with their smartphones right now, he believed more people would do so as more banks came on board.

"It's the way of the future, we're moving to digital everything," he said.

"If people want to use it, we want to accept it. If it makes their lives easier, we're willing to facilitate it."