4. Is there a ban on corporate donations to candidates?

While no ban exists on corporate donations, the donations must be disclosed to the Australian Electoral Commission if it is above a certain threshold. Donations from companies to candidates are listed on the donor transparency register. 

"In Australia, for substantial sums of money across many companies, it is impossible to tell the full amount of political expenditure or the extent to which the expenditure reflects the personal whim or short-term interests of boards or genuinely advances long-term shareholder interests"

 Sources: Australian Electoral Commission:  https://www.aec.gov.au/Parties_and_Representatives/public_funding/threshold.htm (updated 28th May 2019)

Tranparency Register of election donations,  https://transparency.aec.gov.au/Donor

Corporate Political Expenditure in Australia. Howard Pender, Research Director. Australasian Centre for Corporate Responsibility, p.20 June 2016.  

 The financial disclosure scheme was amended with effect from 8 December 2005 to increase the threshold to ‘more than $10 000’. This amount is indexed with effect from 1 July each year based on increases in the consumer price index. The disclosure threshold amount that will apply from 1 July 2019 to 30 June 2020 is more than $14,000. No details of donations less than the threshold allowed by the Australian Electoral Commission are publicly available. 

Source: Australian Electoral Commission:  https://www.aec.gov.au/Parties_and_Representatives/public_funding/threshold.htm (updated 28th May 2019)