The Fair Work ombudsman has secured more than $500,000 back pay for delivery drivers who worked for the pizza chain, Domino's.

A self-audit found that more than 1,600 drivers were underpaid between January 2010 and December 2011.

The most common issue was the underpayment of the minimum hourly rates.

Most occurred at franchise-operated stores, but there were underpayments at stores in every state and territory.

The majority of workers have received the payments, but more than $200,000 is being held in trust for workers who cannot be located.