Should You Pay Down Your Mortgage or Invest? A Practical Guide for High‑Income Australians

If you’re earning a high income, have no bad debts (such as credit cards and personal loans) and have surplus cash each month, the big question becomes: should you put it into the mortgage or invest it? 

Both can work — but the right choice depends on interest rates, tax, time horizon, and your appetite for risk.

1. The Core Rule

Your decision hinges on one comparison:

Is your expected after‑tax investment return higher than your mortgage interest rate?

If yes → investing may build wealth faster.

If no → paying down the mortgage is usually better.

2. Why Paying Down the Mortgage Is So Powerful

Extra repayments give you a risk‑free, tax‑free return equal to your interest rate:

• Mortgage rate 6% = guaranteed 6% return

• For someone on a 45% tax rate, that’s equivalent to earning 10.9% pre‑tax elsewhere
  

No volatility. No tax. No fees. No stress.

3. Why Investing Can Still Win

Long‑term diversified portfolios often return 7–10% p.a., but:

• Returns aren’t guaranteed

• They’re taxable

• You need a long time horizon

• You must tolerate market drops
  

Investing inside super improves the equation (15% tax on earnings, 0% in pension phase), making it more attractive for high‑income earners, particularly if they are closer to retirement age.

4. The Key Factors That Decide the Winner

Interest rate Environment

• Above 6% → mortgage usually wins

• Below 4% → investing becomes more compelling
  

Time horizon

• Under 5 years → mortgage

• 5–10 years → depends

• 10+ years → investing often wins
  

Risk tolerance

• Hate volatility → mortgage

• Comfortable with ups and downs → investing
  

Tax position

• High marginal tax rate → mortgage reduction is very efficient

• Using super → investing becomes more tax‑effective
  

5. The Offset Account: The Flexible Middle Ground

An offset gives you:

• The same interest savings as extra repayments

• Full access to your cash

• The option to invest later
  

For many high‑income households, this is the best hybrid strategy.

6. The Bottom Line

There’s no universal answer — but there is a right answer for your situation.

Choose mortgage reduction if you want:

• Guaranteed returns

• Lower risk

• Simplicity
  

Choose investing if you want:

• Higher long‑term growth

• Are comfortable with volatility

• Have a long time horizon
  

Choose an offset if you want:

• Flexibility

• Liquidity

• Interest savings

Need help deciding?

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The purpose of this blog is to provide general information only and the contents of this blog do not purport to provide personal financial advice.  We strongly recommend that investors consult a financial adviser prior to making any investment decision. The contents of the our blog does not take into account the investment objectives, financial situation or particular needs of any person and should not be used as the basis for making any financial or other decisions. The information is selective and may not be complete or accurate for your particular purposes and should not be construed as a recommendation to invest in any particular product, investment or security. The information provided on this blog is given in good faith and is believed to be accurate at the time of compilation.