Cheap photocopies, altering birth dates, pretending to lose a licence, or using other people's IDs were just some of the tricks used by the nation's youth.
Dunedin police acting alcohol harm reduction officer Senior Constable Ian Paulin said Dunedin police had more than 100 fake licences in their files, with 16- to 17-year-olds the biggest offenders.
"They scratch off their year of birth, change a 1994 to a 1991, that sort of thing," he said.
Peer pressure from older friends to drink often led the 16- and 17-year-olds to alter the dates of an older licence - usually a learner's - before trying to get into a licensed establishment or buy alcohol at an off-licence.
The legal drinking and alcohol purchase age in New Zealand is 18.
"They all just want to get into the bars."
Another ruse was for teenagers to "lose" a licence, apply for a new one and then doctor the duplicate, Snr Const Paulin said.
The licences ranged from flimsy photocopies to dates being scratched off and written over with indelible ink.
"Some are very good; some are very amateur."
Anyone caught would be interviewed by police and issued with a warning, but any second offence would see the offender go through the courts, where they faced a $2000 fine.
There had been one organised case of falsifying IDs, which was before the courts.
Snr Const Paulin said those with the "most to lose" were those in the hospitality industry, and doormen were well aware of the tricks employed to gain entry into their establishments.
If an underage drinker was found on licensed premises after using a fake ID, police would question the establishment's security.
"If they got though their system, we would have to ask why it got through," Snr Const Paulin said.
Hospitality Association New Zealand chief executive Bruce Robertson said it was likely thanks to the industry's vigilance that police were in possession of so many fake IDs.
"Our frustration is that we don't see anything being done about prosecuting those people using these IDs, and of course when police come visiting, those IDs disappear and we wear it for serving someone underage."
If people were prosecuted for using a fake ID, it would make others think twice about doing it, he said.
Snr Const Paulin advised parents to check their children's IDs.
