The former owner-operators of a 7-Eleven store in the Melbourne suburb of Parkville could be hit with fines after allegedly falsifying payroll records and underpaying 12 employees more than $84,000 for a year, including one staff member who was paid $6.25 an hour for some shifts.

The Fair Work Ombudsman launched action against the former store owners, Yiran "Janice" Gu and Haiyao "Harry" Xu, of Balwyn North, and their company Hiyi Pty Ltd as part of a major investigation into the payment practices of 7-Eleven franchisees.

The Parkville 7-Eleven was one of 20 stores raided by the regulator in Melbourne, Sydney and Brisbane in September 2014. It was the third raid of 7-Eleven stores by the regulator in the past six years.

Fair Work Ombudsman Natalie James said preliminary results from the investigation was concerning, with contraventions identified at most of the 20 outlets recently targeted for investigation.