When we did the application sponsors of an applicant with children require police clearances, so I was required to. But I am sure that now all sponsors need them - part of a clamp down on Domestic Violence.
If you have paid your tax, you probably wont have a debt (you might get a fine for late lodgement but they often waive that if you are proactive on fixing the error).
Working under ABN's is very hot at the moment, particularly if through Labour Hire Firms. If your using the ABN then it appears you are paid by an Australian company and paid as an Independent Contractor. If you look up the "Independent Contractor or Employee" decision tool on the ATO web site, there is a very great chance you will find you are an Employee for tax and supa purposes. The penalties for the companies for this can be pretty steep around $50k per offence. It also leads to Payroll Tax evasion. Luckily for you there is no penalty so to speak but the ATO can cancel your ABN.
The short quick fix for this is to open a company and trade under a ACN not a ABN. A bit more to it than that, but have a chat to your accountant about it.
A extract from a email I got this week.
your industry is one where labour hire providers appear to be engaging in sham contracting in order to avoid their obligations, such as their payroll tax requirements, to workers. Through its own investigations, the Government has become aware of many workplaces like yours.