It was also discovered that some receptionists were regularly rostered on annual leave, for a day a week, without any consultation and without having applied for leave.
Labour Inspectorate southern regional manager Stu Lumsden said "the exploitation of workers is not welcome" and breaches New Zealand law.
"This ruling sends a clear message to employers that failure to comply with the minimum labour standards will not be tolerated," he said.
"The ERA found there was a need to impose a penalty to signal a more general deterrence for some employers, or as an encouragement for them to continue to, or to start to, pay employees their minimum entitlement."
Employers who breach the employment law will be subject to enforcement action which can include penalties of up to $10,000 for individuals and $20,000 for companies.
• The Ministry encourages anyone in a similar situation, or who knows of anyone in a similar situation, to call its contact centre on 0800 20 90 20 where their concerns will be handled in a safe environment.