The operators of two sushi kiosks in Cairns underpaid five casual employees almost $50,000 in less than six months, the Fair Work Ombudsman has found.

The workers were short-changed amounts ranging from $7285 to $12,177 as a result of being paid a flat hourly rate of $9 for all hours worked.

This is below the minimum hourly rate and did not take account of penalty rates for weekends and public holidays or casual loadings.

They should have been paid between $22.86 and $30.06 an hour, depending on their shift.

The five employees, three Japanese and two Koreans aged between 21 and 32, were in Australia on working holiday visas.

They worked for the Mizuno Trading Company, trading as Fuji Homestyle Cuisine.

The company has two sushi kiosks at the Cairns Central shopping centre.

The employees prepared Japanese-style food, served customers and cleaned.

The Fair Work Ombudsman commenced an investigation after receiving complaints from the employees.

Following an investigation by the Fair Work Ombudsman, Mizuno Trading has agreed to back-pay the workers in full.

Company director Shoichi Mizuno told inspectors he paid only $9 an hour because that was “all he could afford” and the employees had agreed to this rate.

Mizuno also told inspectors that $9 was the “market rate” for this type of work in Japan.

Fair Work inspectors explained to Mizuno his obligations under federal workplace laws and that the five employees should have been paid rates stipulated under the Fast Food Industry Award 2010.

Mizuno and his company have apologised for the contraventions and agreed to reimburse the employees – who were short-changed for work they performed between April and August last year.

The company will make an upfront payment of $20,000 and then repay the balance in monthly installments over 14 months.

It has also agreed to revamp its workplace policies to ensure future compliance with workplace laws.