(b) That's wrong. A trust can be created without formalities. It can even be created by implication rather than expressly. However, a trust that is created to run a business would normally be created expressly and in writing, by means of an 'instrument' or 'deed' of trust. The proper drawing up of an instrument of trust is important in such circumstances because it is necessary to make provision for various things that may not otherwise be permitted by law, such as giving the trustee authority to carry on a business on a continuing basis; allowing the trustee to be paid for the work done in relation to the trust; or giving the settler the right to terminate the trust.
In addition to the provisions contained in an instrument of trust, trusts are governed by state and territory legislation. Note: A trustee carrying on a business in Australia must obtain an Australian Business Number (ABN) and comply with the Business Names Registration Act 2011 (Cth).
A trustee of a trust that is carrying on a business can register for GST purposes.