Question 1

Should I put money in a mortgage offset account or invest in shares in Australia?

Accepted Answer

The offset earns your mortgage rate tax-free and risk-free. A common heuristic is: hurdle = mortgage rate divided by (1 minus marginal tax rate). But for a PPOR this formula overstates the required share return because it treats all investment gains as taxed annually — shares are not. Capital gains are deferred until sale and receive a 50% CGT discount after 12 months, and franking credits offset dividend tax. The effective break-even return is well below the formula suggests. This calculator runs a year-by-year FIFO CGT simulation so you can see the real after-tax comparison for your own numbers.

Question 2

What is cashflow neutrality in an offset vs shares comparison?

Accepted Answer

Cashflow neutrality means all three scenarios cost the same amount per year out of pocket, making them genuinely comparable. The anchor is Scenario B's full P&I repayment. Scenario A invests the repayment saving into shares each month. Without this constraint you would be comparing different levels of financial commitment, not different strategies.

Question 3

What is the hurdle rate for offset vs shares in Australia?

Accepted Answer

The hurdle rate heuristic is: Mortgage Rate divided by (1 minus Marginal Tax Rate). At 6% and 37% tax that gives 9.5%. However, this formula treats shares like a savings account taxed annually in full — it ignores that capital gains on shares are deferred until sale and receive a 50% CGT discount after 12 months, and that franking credits offset dividend tax. These factors significantly reduce the effective tax drag, making the real break-even share return well below the formula's output. The formula is accurate for an investment property (where the offset's benefit is rate times (1 minus tax)), but not for a PPOR.

Question 4

How do franking credits affect the offset vs shares comparison?

Accepted Answer

Franking credits attach to fully franked dividends from Australian companies. Individuals can claim them as a tax offset or refund. Super funds at 15% tax rate receive a large portion back as cash. This materially improves the after-tax return of Australian shares versus the theoretical hurdle rate.

Question 5

What is the Power Play scenario in the offset calculator?

Accepted Answer

Power Play puts a lump sum into the offset account and maintains the original full P&I repayment. Since less interest is charged each month, the entire interest saving goes directly to principal — a compounding snowball that can reduce a 25-year loan by 8 to 12 years with no extra cash outlay. It is the maximum guaranteed risk-free outcome.

Question 6

Can I use a super fund tax rate in the offset vs shares calculator?

Accepted Answer

Yes. Select Super Fund (15%) as your investor type. The calculator applies a 15% dividend tax rate and 33.3% CGT discount for assets held over 12 months, significantly improving the after-tax share return compared to a 37% or 45% individual rate.

Question 7

Should I put money in my offset account or invest in shares in Australia (2026)?

Accepted Answer

At a 6.3% mortgage rate and 37% marginal tax rate, the tax-free offset return is 6.3%. To beat that with shares after CGT and income tax, you'd need a gross return of approximately 7.5–8.5% depending on your holding period and franking credits. The ASX 200 has averaged around 9–10% including dividends historically, so shares have historically won for most investors with a 10+ year horizon — but with significantly more volatility and risk. Use this calculator to model your exact numbers and see the year-by-year comparison.

Question 8

How does the mortgage rate affect the offset vs shares comparison?

Accepted Answer

The higher the mortgage rate, the stronger the offset account's guaranteed return. At 5% the offset returns 5% tax-free and risk-free — shares need to significantly outperform to compensate for risk. At 7% the offset's guaranteed return becomes hard to beat reliably. At low rates (2–3%), shares are clearly superior for most investors with a long horizon and moderate tax rate.

Question 9

What is the Monte Carlo simulation in this offset vs shares calculator?

Accepted Answer

The Monte Carlo simulation runs 1,000 scenarios where annual share returns vary randomly each year using a distribution calibrated to your expected return and historical volatility. It shows the range of possible outcomes for investing in shares versus the certainty of the offset account return. The probability that shares outperform the offset is shown as a percentage — a key insight for risk-aware decision making.

Question 10

Does paying down the mortgage or using an offset account produce the same result?

Accepted Answer

No — there is an important difference. Extra repayments permanently reduce your loan balance and cannot be accessed again without refinancing. Money in an offset account reduces interest exactly the same way, but remains accessible as a liquid emergency fund or investment opportunity fund. For most borrowers, offset is superior to extra repayments because you get the same interest saving with full access to your cash.

Question 11

How does negative gearing affect the offset vs shares comparison for investment properties?

Accepted Answer

For an investment property, the offset account's effective after-tax benefit is reduced because mortgage interest is tax-deductible — so the net interest cost is rate × (1 − tax rate). A 6.3% mortgage at 37% tax effectively costs 3.97% after deductions. This makes it much easier for shares to beat the offset on an investment property than on a PPOR, where no interest deduction applies.

Offset vs Shares Calculator 2026 (Australia)

How this four-scenario model works

Cashflow Neutrality (the key principle)

The four scenarios

The hurdle rate formula (and why it's a heuristic, not a hard rule)

Monte Carlo methodology

Tax treatment

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