5 Ways to Pay Off Your Investment Mortgage Faster
- Only accelerate if your strategy is deleveraging — negatively geared holders may do better with an offset.
- Fortnightly repayments save ~4 years; a consistent offset ~3-4 years; annual lump sums ~6 years.
- Pay non-deductible home loan debt first, then recycle equity as deductible splits.
- These strategies interact — combined effect isn't additive, so model the after-tax result before committing.
Paying down an investment loan faster is not always the right call. If you are negatively geared and holding for capital growth, redirecting cash into an offset can beat principal reduction on an after-tax basis. But if your strategy is deleveraging toward retirement or an SMSF drawdown phase, the numbers below are worth modelling before you commit.
All examples assume a $600,000 loan at 6.5% over 30 years, interest-only converting to P&I unless stated. Your figures will differ, but the relative impact holds.
1. Switch from interest-only to P&I earlier than the bank forces you
Most investors ride the interest-only period to its five-year limit, then extend, then extend again. Every year you delay principal repayment pushes the full amortisation into a shorter, more expensive window.
On the $600,000 loan, starting P&I immediately instead of after a 10-year IO stretch means your first repayment includes roughly $700/month of principal from day one. Across the loan, moving off IO ten years earlier clears the debt around 8 to 9 years sooner than the stacked-IO path, because you stop compounding the same balance.
The trade-off is real: your deductible interest falls and your cash flow tightens. This is exactly the sort of decision worth running as a side-by-side forecast before you sign the variation.
2. Fortnightly repayments instead of monthly
This one is close to free. Pay half your monthly repayment every fortnight and you make 26 half-payments a year, which equals 13 monthly payments instead of 12. The extra month goes straight to principal.
On the $600,000 P&I loan at 6.5%, fortnightly repayments knock roughly 4 years off a 30-year term and save around $130,000 in interest. Confirm your lender calculates it as true fortnightly and not “monthly divided by two, paid monthly” dressed up in new language. Some do the latter and the benefit vanishes.
3. Direct all rent and tax refunds into an offset
If you hold the property in your own name and claim negative gearing, your annual tax refund on a $22,000 interest bill plus depreciation can easily run $8,000 to $12,000. Parking that in an offset against the investment loan, rather than spending it, has the same effect as an extra lump-sum repayment without touching redraw flexibility.
Route the rent through the offset too. An offset holding an average $25,000 balance against a 6.5% loan saves about $1,625 a year in interest. Do that consistently and you take 3 to 4 years off the term, while keeping the cash accessible if you need it for the next acquisition.
4. Recycle equity, but pay down the non-deductible debt first
If you carry a home loan and an investment loan, the fastest legitimate acceleration is debt recycling: pay principal aggressively against your non-deductible home loan, then redraw that equity as a separate split to invest. You are not paying the investment loan faster in dollar terms, but you are converting non-deductible debt into deductible debt and clearing the expensive, non-refundable interest first.
Structured cleanly with separate splits so the ATO can trace purpose, a household with a $400,000 home loan and $600,000 investment loan can typically clear the non-deductible portion 5 to 7 years faster than paying both down proportionally. Get the loan splitting right at settlement; retrofitting it is messy.
5. Annual lump sums from a genuine surplus
A single $10,000 lump sum in year one of the $600,000 loan saves more than a $10,000 lump sum in year 15, because it compounds against the balance for longer. One $15,000 payment in year two saves roughly 14 months. Making a $10,000 payment every year from a real surplus, not borrowed money, clears the loan around 6 years early.
The discipline is knowing your surplus is genuine. Actuals tracking against your forecast tells you whether that “spare” $10,000 survives the strata special levy and the vacancy you did not budget for.
Model it before you commit
None of these move in isolation. Fortnightly payments plus an offset plus one annual lump sum interact, and the combined effect is not additive. Run your actual balance, rate, and holding period through a projection so you can see the after-tax result rather than the headline interest saving.
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