Pay Off Mortgage or Invest? The Honest Australian Guide

The core trade-off: guaranteed vs expected return🔗

When you make an extra repayment, you earn a guaranteed, risk-free, after-tax return equal to your interest rate. At 6%, that is effectively 6% on every dollar, with no volatility, no tax event, and no chance of losing it. No investment can promise that. The alternative, a broad index ETF like VAS or VGS, has historically returned around 9% to 10% a year for Australian shares over the long run, but that return is not guaranteed, not tax-free, and comes with real volatility (shares fell around 40% in 2008 and 35% in weeks in early 2020).

So on paper investing wins, but only on average and only if you can stay invested through the drops. The real question is whether you will accept risk and tax drag in exchange for a higher expected return, or whether the certainty of the mortgage payoff is worth more to you.

The tax angle: why it is closer than it looks🔗

This is the bit most articles skip. Mortgage interest on your own home is not tax-deductible, so every dollar of interest you save is a genuine after-tax saving worth a full dollar to you. Investment returns, by contrast, are taxed: dividends at your marginal rate (softened by franking credits), and capital gains at your marginal rate but with the 50% CGT discount if you hold for 12 months or more.

Run $10,000 at 8% gross: a top-bracket earner nets about 4.24% on dividends, which does not beat a 6% mortgage, but about 6.12% on discounted long-term capital gains, roughly level with it. A 32.5%-bracket earner does better on both. The upshot: tax narrows the advantage of investing sharply for high earners, but over a long horizon where most of the return is capital growth, investing still tends to win, especially for lower brackets.

The offset account: the overlooked third option🔗

Before choosing between repaying and investing, there is a third option most people underuse: the offset account. Its balance offsets your loan principal, so you only pay interest on the difference, an interest saving exactly equal to your mortgage rate, guaranteed and after-tax, with the money still fully accessible (unlike extra repayments, which may not be redrawable). Keeping the loan balance high while holding cash in offset also preserves the future deductibility of that interest if you ever turn the home into an investment property. Our offset vs redraw guide and offset calculator show the saving in dollars.

Super as a third option: tax-effective but locked away🔗

If you are in the 37% or 47% bracket, salary sacrificing into super is worth a hard look. Concessional contributions are taxed at just 15% going in (versus your marginal rate up to 47%), earnings inside super are taxed at 15%, and the concessional cap is $30,000 a year for 2025-26 (including employer SG). Sacrificing $10,000 on a $150,000 income saves roughly $3,200 in tax immediately, a guaranteed 32% "return" before the money is even invested. The catch is real: super is locked until preservation age (currently 60), and very high earners (income over $250,000) pay an extra 15% via Division 293. See our salary sacrifice super guide for the detail.

The sleep-at-night factor🔗

The maths is only half the answer. Paying off the mortgage gives a guaranteed, tangible outcome, and many people sleep better for it. There is nothing irrational about valuing certainty. Investing, meanwhile, demands discipline that is easy to underestimate: the money has to actually go into the market and stay there through downturns. If you would spend the surplus rather than invest it, or panic-sell in a crash (selling at the bottom is the most destructive thing you can do to a portfolio), the guaranteed mortgage payoff wins by default. Sequence-of-returns risk also matters more the closer you are to retirement, which tilts the balance towards certainty.

Foundations first🔗

Before you even ask the question, cover the basics. Clear high-interest non-mortgage debt first (credit cards at 20% or personal loans at 12% beat any investment return), and build an emergency fund of 3 to 6 months of expenses, ideally in your offset account so it saves interest while staying accessible. Only once those two boxes are ticked is the repay-vs-invest question worth asking.

A worked example: $1,000 a month over 20 years🔗

Illustrative figures, $500,000 loan at 6%, $1,000 a month spare. Extra repayments would clear the mortgage well before term and save roughly $240,000 in interest, leaving you debt-free with a guaranteed, after-tax result. Investing that $1,000 a month at 8% for 20 years grows to about $589,000 before tax, or roughly $520,000 to $540,000 after tax (32.5% bracket, blended with the CGT discount).

On average, investing wins on paper here. But it requires discipline, tolerating real volatility, and paying tax along the way, while the repayment path is certain. Most people do best with a split. You can model both sides with our compound interest calculator.

Which path fits you?🔗

Lean towards repaying (or offset) if your rate is above 6%, you are close to retirement, you would not reliably invest, or you value certainty. Lean towards investing if your rate is low, your horizon is long, you have discipline and a lower tax bracket. Consider extra super if you are a higher earner with a long time to preservation age. And remember it is rarely either/or: a common, sensible split is a well-funded offset, some surplus to investing in a fund like VDHG, and extra super on top when the tax saving is compelling.

Frequently asked questions🔗

Sources🔗

1. ASIC Moneysmart, mortgage calculator and home loan guidance, moneysmart.gov.au
2. ASIC Moneysmart, investing basics, moneysmart.gov.au
3. ATO, concessional contributions cap, ato.gov.au
4. ATO, CGT discount, ato.gov.au
5. RBA, Australian equity market facts 1917-2019, rba.gov.au

General information only, not personal financial advice. Figures are illustrative and outcomes depend on your rate, tax situation and returns. Consider speaking to a licensed financial adviser about your own situation.