You do not have to pay taxes on the interest paid to your father; that is an expense, not income. (money.stackexchange.com)
When you invest through a taxable account you have to plan for income tax on interest earned, along with capital gains tax, and dividend tax. (novelinvestor.com)
If they had let the company hold on to the money, and distribute it as monthly income, they would've had to pay tax on the interest earned. (investopedia.com)