Bonus season, tax refund, an inheritance, a good year, however the lump sum arrives, the question is the same: what’s the smartest thing to do with it? The internet offers three loud, confident, contradictory answers. Here’s the honest version, where the maths actually points, and why.
The three options
You’ve got a lump sum, say $20,000. Broadly, three homes for it:
- Offset account, park it against your mortgage, reducing the interest charged, while keeping it accessible
- Extra repayment, pay it directly onto the loan principal, reducing the balance permanently
- Invest it, shares, ETFs, super, or property, aiming for a return higher than your loan rate
Each has a genuine case. Which wins depends on your loan rate, your tax position, your risk appetite, and how much you value access to the money.
Option 1: Offset (the strong default)
Money in your offset reduces the interest charged on your loan, dollar-for-dollar. If your loan rate is 6.4%, $20,000 in offset saves you roughly $1,280 a year in interest.
Crucially, that saving is effectively tax-free, it’s reduced interest, not earned income, so there’s nothing to declare. To match a 6.4% tax-free saving with an investment, you’d need a pre-tax return of roughly 9-11%, depending on your tax bracket (higher earners need more, since the tax take is larger). And unlike a repayment or an investment, the money in offset stays fully accessible, you can pull it out anytime for an emergency, a renovation, or the next opportunity.
For most homeowners, this combination of a strong guaranteed return, tax-free, fully liquid, makes offset the sensible default. See how to use an offset account properly for the mechanics.
Option 2: Extra repayment (same saving, less flexibility)
Paying the lump sum directly onto your principal saves you exactly the same interest as offset, at the same rate. The difference is access.
Once the money’s on the loan, getting it back requires a redraw (if your loan allows it) or a refinance. For borrowers who worry they’d spend money sitting in an offset, a direct repayment enforces discipline. But for most people, offset delivers the identical interest saving and keeps the money available, which is why offset usually edges it out.
The exception: some fixed-rate loans have limited or no offset, in which case extra repayments (up to the annual limit) may be the best available lever.
Option 3: Invest (higher ceiling, higher risk)
Investing the lump sum, in shares, ETFs, or additional super contributions, has the highest potential return. Over the long run, diversified investments have historically returned more than mortgage rates.
But there are three catches. First, investment returns are taxed, so the after-tax return is lower than the headline. Second, investing carries risk, returns aren’t guaranteed, and markets fall. Third, the offset saving is a guaranteed 6.4% (or whatever your rate is), tax-free, which is a genuinely high bar for a risk-based investment to clear after tax.
The honest rule: investing beats offset only if you reasonably expect an after-tax return above your loan rate, and you’re comfortable with the risk and the longer time horizon. For some people, especially with a long horizon and higher risk tolerance, it’s the right call. For many, the guaranteed tax-free offset return is hard to beat.
Not sure which move fits your situation? A 15-minute call weighs your loan rate, tax position, and goals, and points you to the option that genuinely serves you best.
Book a 15-min call -> · 0461 117 777
A quick way to decide
Run through these in order:
- Do you have high-interest debt (credit cards, personal loans)? Clear that first, nothing beats eliminating 20% interest. See rolling debt into your mortgage.
- Do you have an adequate emergency buffer? If not, the offset doubles as your buffer, put it there.
- Is your loan rate high relative to safe returns? If yes (usually the case), offset is the strong default.
- Do you have a long horizon and appetite for risk? If yes, investing a portion can make sense, often alongside, not instead of, the offset.
Many people do a blend, most in offset, some invested, which balances the guaranteed saving with long-term growth.
The bottom line
For most homeowners, the honest maths favours the offset account: a strong, guaranteed, tax-free return with full access to your money. Extra repayments match the saving but lock the money away. Investing has a higher ceiling but comes with tax and risk. There’s no universal answer, only the one that fits your rate, your tax position, and your appetite for risk.
To work out your best move, book a 15-minute call with Harbir.
Or call 0461 117 777 | Email info@creditstar.com
Frequently Asked Questions
Q1. Should I put my bonus in my offset or pay off my mortgage?
Ans. Both save the same interest at your loan rate. Offset keeps the money accessible; a direct repayment locks it away. For most people, offset wins because of the flexibility.
Q2. Is it better to invest or put money in my offset?
Ans. Offset gives a guaranteed, tax-free return equal to your loan rate. Investing has a higher potential return but is taxed and carries risk. Investing only wins if the after-tax return reliably beats your loan rate.
Q3. How much interest does money in an offset save?
Ans. At a 6.4% loan rate, $20,000 in offset saves roughly $1,280 a year, and it’s tax-free because it’s reduced interest, not income.
Q4. Why is the offset saving tax-free?
Ans. Because it reduces the interest you’re charged rather than earning you income. There’s nothing to declare, unlike interest from a savings account or returns from an investment.
Q5. What return would an investment need to beat my offset?
Ans. To beat a 6.4% tax-free offset saving, an investment would need roughly 9-11% before tax depending on your marginal tax rate, higher earners need the most. That’s a high bar for a risk-based return to clear reliably.
Q6. Should I clear credit card debt before using my offset?
Ans. Yes. High-interest debt (18-22% on cards) costs far more than your mortgage saves. Clear that first, then decide between offset, repayments, and investing.
Q7. What if my fixed loan doesn’t have an offset?
Ans. Then extra repayments (up to the annual limit) may be your best lever. Some fixed loans allow only partial offset or none, so check your product.
Q8. Can I split my lump sum across options?
Ans. Yes, many people do. A common blend is keeping most in offset for the guaranteed saving and liquidity, while investing a portion for long-term growth.
Q9. Does putting money in offset reduce my loan term?
Ans. Effectively yes, by reducing the interest charged each month, more of your repayment goes to principal, which shortens the loan term without changing your repayment.
Q10. Is paying down the mortgage always the safe choice?
Ans. It’s a guaranteed, risk-free return equal to your loan rate, which is genuinely strong. Whether it’s “best” depends on your goals, but it’s rarely a bad choice.
This guide is general information only and doesn’t take into account your personal situation, and it isn’t financial or investment advice. For advice specific to your circumstances, consider a licensed financial adviser, and for your loan, book a call with Harbir Hundal, Credit Representative 506564 of BLSSA Pty Ltd ACN 117 651 760, Australian Credit Licence 391237.
