As a trustee of your SMSF, you're responsible for making sure no conflict of interest arises.
To avoid a conflict of interest, section 109 of the Superannuation Industry (Supervision) Act requires you to make and maintain investment transactions on an arm’s length basis. This means your SMSF can't carry out transactions with related parties of the fund. For example, you can't use your SMSF to buy your residential home.
There are, as always, some exceptions. In some circumstances, you can use your fund to carry out a transaction with a related party as long as the transaction is made on a commercial (arm’s length) basis. For example, your fund can purchase your business property and rent the property back at a commercial rent.