Staff at the clothing retailer Cotton On are being urged to check their pay after $35,000 worth of underpayments were discovered at the company's Auckland distribution centre.
First Union transport and logistics secretary Jared Abbott said the underpayments - in some cases of up to $4000 - affected about 30 workers.
"Often people not getting paid for hours they work, miscalculation of annual leave, not getting paid correctly for breaks or for overtime that they have worked."
Mr Abbott said the problem was likely company-wide and he wanted all staff at the Australian-owned company to check their pay.
He said it was not the first payroll problem at Cotton On, which was forced to repay $80,000 in underpayments to staff last year.
Cotton On said when the error was identified, staff that had been affected were reimbursed immediately.
The company said its payroll audit showed 41 staff were underpaid and 10 were overpaid.
It reimbursed staff a total of $35,000 in back payments, and was working to prevent future mistakes.