The Statutory Interest rate for loans as set by the ATO is currently 7.4%. Many service providers will charge interest on unpaid accounts at 2-3%, some will use the current ATO statutory rate, and others will charge up to 10%, as well as a late fee.
You are allowed to charge late fees and/or interest on your unpaid bills, if:
1. it is in the Terms and Conditions that the customer has already signed prior to you providing the product or service, and;
2. certainly it was known and agreed before any credit was extended to the client, and
3. so long as the charge is within what would be deemed “fair and reasonable” if it were brought in front of a magistrate.
- See more at: http://www.sjbookkeeping.com.au/over....grdJKBQI.dpuf