The worker is one of nine across the Illawarra back-paid a total of $23,400 following intervention by the Fair Work Ombudsman.

The Wollongong worker was underpaid the minimum hourly rate and overtime rates between 2009 and 2011, as well as wages in lieu of notice and annual leave entitlements upon termination of employment.

Part of the underpayment resulted from the employer failing to pass on July 1 pay rate increases.

In another case, eight workers at a Shellharbour cafe were back-paid $11,400 after being underpaid the minimum wage rate, as well as penalty rates for weekend, early morning and late-night work over a 12-month period in 2011-12.

Acting Fair Work Ombudsman Michael Campbell said the cases highlighted the need for employers to be aware of the wages and entitlements payable to their staff.

In both cases, the underpaid employees were reimbursed all money owed without the need for the Fair Work Ombudsman to take further action.

Mr Campbell said Fair Work inspectors had also helped the offending employers to put processes in place to ensure the errors did not occur again.

"When we find mistakes, we're here to assist and help employers understand their obligations to ensure they comply in the future," he said.

Workers or employers seeking support should contact the Fair Work Ombudsman via fairwork.gov.au or phone 13 13 94.