Your teen's brain will continue developing until their mid 20s. Critical areas that help them with learning, planning, emotional stability and memory are all still growing and forming. This means your teen is particularly vulnerable to long-term damage caused by underage drinking and the safest option for them is to abstain from drinking alcohol until they're at least 18. We all know that in New Zealand it's illegal for anyone under 18 to buy alcohol, however there is no age at which it is illegal to drink alcohol in New Zealand.