Compare two different benefits
Extra mortgage repayments produce a return equal to interest avoided, with no market volatility, and can improve cash flow once the loan is smaller. Extra super contributions may receive favourable tax treatment and long-term investment growth, but returns are uncertain and the money is generally preserved.
The better use of a dollar depends on the mortgage rate, tax position, contribution type, years to retirement, emergency savings and comfort with debt and investment risk. A headline comparison between an average market return and today’s loan rate leaves out most of those facts.
Protect liquidity first
Money paid into super is normally unavailable for a broken car, lost job or mortgage arrears. An offset account can reduce home-loan interest while keeping cash accessible, although fees and loan terms matter. Build an emergency buffer before locking every spare dollar away.
Check for expensive consumer debt and minimum repayments as well. Paying 20% credit-card interest while salary-sacrificing aggressively is unlikely to be a coherent household plan.
Use a split strategy when certainty is impossible
You do not have to send all surplus cash to one destination. A split can build retirement savings while reducing debt and preserving flexibility. Set an amount or percentage for each, then review after rate changes, pay rises or major life events.
Model after-tax cash flow and contribution caps, not just the future balances. People close to retirement should also consider how mortgage debt will be serviced if employment ends earlier than planned and whether using a lump sum later would leave enough super for income.
Quick reference
Key things to remember
- Start with an emergency buffer and expensive debt.
- Compare after-tax mortgage interest with expected after-fee, after-tax investment returns.
- Consider contribution caps and access restrictions.
- A split strategy can balance certainty and long-term growth.
Put it into practice
Your next steps
- 01
Write down your mortgage rate and redraw or offset terms.
- 02
Estimate the tax treatment of the proposed super contribution.
- 03
Model optimistic and conservative investment outcomes.
- 04
Choose a repeatable amount rather than relying on a perfect forecast.
Check the source
Official information
Super and tax rules change. These primary sources are the right place to verify the details before you act.