This happened to me last year.
Just leading up to Christmas I received a nasty letter stating that I owed around 1200 dollars.
This was a result of the centrelink glitch, same as everyone else on here. Between working roles I was on the dole for about 2-3 months of that year.
Anyways I ended up finding work that year and as a result i was presented with this debt. I spoke to centrelink over the phone and they told me I had to produce pay slips for that year clearly stating the time i stopped work and started again.
Because it was so long ago I did not know which contracting agency i was with. So I couldn't begin the process of contacting them and asking for pay slips etc.
While I was on the phone to centrelink they actually mentioned the employers I had for that year and by process of elimination I was able to find out which agency I was with.
By the act of god they were still in business (unlike a few of the other contract agencies I was employed by during this time period). They were able to email my payslips and I provided them to centrelink and they reversed the debt so I didn't owe them anything.
I pay my taxes in the hopes that when I am down in life and unemployed I can depend on the system to support me.
I have only ever been on centrelink for 3 months of my life and the one time I leaned on them for support I actually ended up owing them money.
Which is the complete opposite effect of what a support system should function as.
I am just thankful I was able to prove my innocence and my debt was cleared.