Supplier loans; as the ATO is viewed as a supplier you may obtain a supplier loan to pay the ATO debt. However, these supplier loans are best for loans that are paid off in no more than 6 months. Therefore, they may not be a suitable option if you are seeking a longer loan term.
Unsecured business loans; these loans are not secured by the property. However, they usually have an option for a caveat or unregistered mortgage. Although, this may only be lodged in the event that the loan goes into default or payments are not made.
Invoice factoring finance where you are able to obtain finance against unpaid invoices. However, you would need to ensure you had sufficient future revenue or working capital to meet your obligations. As you would forego the future business cash flow from that invoice.