Registering your business and getting your own unique 11 digit Australian Business Number means:
Other businesses can identify you to confirm invoices and ordering
You can claim goods and services tax (GST) credits
You may be able to avoid pay as you go tax (PAYG) on payments you receive
If you're eligible, you may be able to claim energy grants and credits
You can register a '.com.au' domain name for your email address and website
If you don’t register your business other entities that you invoice may be required to withhold 47% for tax purposes from payments they make to you.