The scanners, which recognise 3000 forms of picture ID, have been welcomed by police but the Hospitality Association said it would need to investigate the privacy issues around the devices before giving them their support.
For now, the system helps Danny Doolan's identify people who have already been refused or kicked out, said owner Geoff Tuttle.
"Because it can get so dark and so packed in here, it was really good for pointing out repeat offenders."
Mr Tuttle said the scanner recognises fake IDs, keeps track of the number of punters and increases the safety of everyone in their bar.
Danny Doolan's uses the machine on Friday and Saturday, when up to 700 people pass through the doors.
The Prospect of Howick owner, Barry O' Shaughnessy, said: "We have a regular crowd of young people who like to come here, so word spreads fast around the under-agers that they're not going to get in."
ID Scanners' director, Thomas Rawson, said: "It makes every person that goes into a venue accountable for their actions ... and it will only become more effective as more bars pick it up."
Mr Rawson said people were able to have their details removed from the system by writing to the bar or his company directly, as long as there had not been an incident.
He said the system was voluntary but a venue may decline entry if subjects refused the terms.
The Hospitality Association's Jill Davey said one of the key issues was around people's privacy.
The Privacy Commissioner's office said bars had to be clear exactly why they were doing it and should not hold on to information longer than necessary. In addition, anyone who does not need to see the scans should not have access to them.
