So, i have a friend who has no PPOR, getting minimal interest in a savings account say 2.5% which is then taxed at 48.5%. He is wanting to loan me money so i can sit it in my offset account against my PPOR, which has a interest rate of 4% currently. Would not have to pay tax on this return either as it is merely reducing interest payments. From a tax perspective, is this fine for him to loan me say 100k, transfer account to account, and then i transfer him back a later date? Do i need a loan agreement? Please disregard issues with the inherent risk of my friends investment itself - eg unsecured loan, me leaving the country, me being sued.