DO NOT PAY YOUR DEBT. Appeal, appeal, appeal.
I received a call from a debt collection agency in February and was told that I owed just under $6k from a period of 5-6 years ago. I have since done a lot of research into the issue (as I imagine most people have) and have a good understanding of how this stupid robo system works.
I initially provided monthly payslips to counter what they were assuming and that reduced it to $2k. I then asked for all for all of the calculation records used to determine my fortnightly entitlements.
I am very fortunate in that I still have access to my previous employers internal website and can determine on what days I worked. I was casual and a student so this fluctuated wildly, something this messed up debt-system doesn't account for.
I would encourage you to look at the 'fortnightly benefit' periods they have specified. Providing monthly payslips will help (as I learnt) but they still do not directly match up with fortnightly periods centrelink use and therefore their robo-machine still has to make assumptions. If you can, figure out exactly how much you earnt in each of their fortnightly periods and send that through.
I cannot understand how this is still an acceptable process. It prays on the vulnerable and is presuming people are guilty until proven innocent. Using an annual earnings and portioning it across fortnightly pay periods is an absurd approach that is fundamentally flawed when you're talking about people who are earning on a casual basis.
This is an incredibly lazy approach and is WITHOUT A DOUBT resulting in many people paying a debt that they do not in fact owe.