A Kāpiti company contracted to CourierPost has to pay more than $37,000 for breaches of employment law "exploiting vulnerable migrant workers".

Dhanoa Transport Limited and sole director Arvinder Singh Dhanoa were fined $12,000 and $4,000 respectively by the Employment Relations Authority.

But Dhanoa said the mistakes happened because, as a migrant himself, he didn't have the legal advice and knowledge needed.

Labour inspectorate regional manager Kevin Finnegan said in a statement that finding such poor practices connected to a well-known brand, like CourierPost, raised questions about the quality of their systems.

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"It may be troubling for Kiwi customers to find that, while they thought they were making use of a trusted brand, they were in reality engaging with a company exploiting vulnerable migrant workers."

Employees were paid $21,640 in arrears related to breaches of minimum wage and holiday pay, with the penalty also reflecting failure to keep compliant records, or provide employment agreements, the statement said.

The breaches included failure to pay workers, including recent Indian migrants, for tasks such as preparing the vehicles for delivery, which could take up to two hours every day.

Finnegan said MBIE was glad to see Dhanoa had taken steps to be compliant, and repaid affected employees.

Sole director Arvinder Dhanoa said he had a "limited voice" and understanding as a migrant himself. He had moved to New Zealand in 2009, he said.

"It was lack of knowledge and not having proper legal advice. No proper knowledge."

Dhanoa said he felt really bad for the employees and what had happened through the business.

"In my life, I am a really fair person, and I want to do things fairly."

The situation was complicated, but his current employee had told him he was a good employer, he said.