The multinational company paid back affected workers $5.4 million between September and November last year after discovering the error.

“The issue arose because some individual contracts had not been correctly benchmarked against the entitlements in enterprise agreements,” a spokesperson told the Bendigo Advertiser.

“After discovering the issue last year we engaged external experts from Deloitte to conduct a detailed review of all our payrolls, including historical records, in order to accurately identify those affected and assess any back pay owing.

“The major workplace unions were advised at an early stage and consulted on the best way to rectify the issue.”

Read more about Thales: 75 years of manufacturing history celebrated

The spokesperson said individual calculations were made for each employee on back pay owed, including superannuation and interest.

The Fair Work Ombudsman was also notified.

A Fair Work Ombudsman spokesperson confirmed Thales made contact with the ombudsman last year in relation to “non-compliance issues”.

“The Fair Work Ombudsman is making its own independent enquiries in relation to this matter and the company has been assisting with those enquiries,” the spokesperson said.

The Thales spokesperson said the company was sorry the error had occurred and was determined to ensure it did not happen again in the future.

“We are now examining records for staff who have left the company to determine whether any payments are owing to former employees, with the process expected to be finalised by March,” the spokesperson said.

The company employs about 3700 people in Australia.

Any employees seeking advice or assistance can contact the Fair Work Ombudsman via the website or the Fair Work Infoline on 13 13 94.

An interpreter service is available by calling 13 14 50.

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