Unregistered builders may, as a rule, not carry out any building work.

There are some, very limited , exceptions to this rule.

1. No registration is needed whenever a person is a subcontractor to a registered building practitioner.
   
2. A builder who is solely engaged in the business of carrying out domestic building work if the cost of the domestic building work carried out by that person is $5,000.00 or less, in each case. (But a demolisher and a reblocker must be registered for all work, even under $5,000.00).

See also http://www.mbav.com.au/vpLink.aspx?ID=8081