An ABN - an Australian Business Number - is what genuine independent contractors use to run a business and get paid.
If your boss forced you to use or to get an ABN, that could mean the boss is trying to avoid paying your lawful pay and conditions.

If your employer expects you to do the job personally (and you can't send someone else to do it instead) that may mean that you are an employee.

If the company provides your tools, PPE, vehicle or materials, that suggests you may be an employee.

Independent contractors can typically control how to do their work. If your employer directs you how to do the work, you may be an employee.

If your employer sets your working hours, and you have to attend work during those hours, you may be an employee.
Does the employer set your roster?
Can you say 'no' to shifts or tasks?
Can you choose when the work will be done?

Genuine contractors run their own business and usually have more than one client.
If you are not able to do work for different companies when you decide, that indicates you may be an employee.

If it looks like you're part of the company - that's a sign you should be an employee of that company.

If you're on an ABN, but you're doing the same or similar work as your boss's employees - then it's likely you should be an employee too.