As the end Australian financial year draws to a close on 30th June, it's time to make arrangements to pre-pay up to 12 months interest on my margin loans. I owed $116K to Comsec, so I prepaid the next 12 months interest on $100K of the balance. I also took up the option to capitalise the prepaid interest. I had some other funds sitting in online savings accounts, so I used that money to repay the remaining $16K of variable rate margin loan. This will mean that I don't have to make monthly interest repayments on the Comsec account for the next 12 months.
I expect I'll soon receive the paperwork to prepay interest on my other margin loan account with Leveraged Equities. I currently have $150K prepaid with them, which I'll reduce to $140K as I have around $6K sitting within the cash management account in my LE due to recently selling my Qantas shares. I'll put that money towards the interest prepayment, so I'll only have to come up with another $6K for the interest prepayment. This will leave only a few thousand dollars of margin loan debt requiring monthly interest payments.
One benefit of making the interest prepayment is that you get a slightly lower interest rate than the monthly variable rate (but this is offset by the opportunity cost of the prepaid interest amount for an average of 6 months). But the main benefit is that you bring forward the tax deductible interest expense by 12 months, so you gain an extra tax deduction the first year you do this. However, each subsequent year you are simply using the prepayment of the next year's interest to substitute for the current year's interest (that was prepaid the previous tax year). At some time in the future you have to unwind the prepayment arrangements by having a year with no tax-deductible interest payment, or possibly a series of years with slowly decreasing interest deductions. I plan to schedule this to occur when I'm retired and over 60. At that time (under the new Simpler Super rules) I'll be living off tax exempt Superannuation pension income, so the tax I pay on any dividend income from my margin loan portfolio will be very low, so getting the tax deduction for interest payments will no longer matter.
Anyhow, interest prepayment on margin loans is just the "icing on the cake" - the main benefit of using margin loans is to get a bigger stock portfolio, but have tax deductible interest payments slightly larger than the dividend income from the portfolio. This basically means that you have no net taxable income from the stock portfolio, and instead only make capital gains on the portfolio. If the gains are on assets held more than 12 months before sale, the applicable tax rate is half your marginal tax rate.