Those aged under 18 are legally entitled to just 70% of the minimum rate.
There are calls for younger people to be paid the higher minimum wage rate.
A new ESRI report shows 15,000 young workers are being paid below minimum wage.
Also contained in this ESRI research is the positive news that around three quarters of those under 20 are actually paid the full rate.
The current minimum wage rate is €11.30 an hour which will rise to €12.70 in January.
Those aged under 18 are legally entitled to just 70% of that rate, where as 18 year olds are entitled to 80% of the rate and those aged 19 are entitled to 90% of it.
However, the National Youth Council of Ireland thinks that doesn't go far enough. The organisation is joining calls for young people to be paid the higher rate.
Legislation in Ireland also exempts apprentices, people employed by a close relative, and prisoners from earning the full minimum wage currently.