Mortgage Offset vs Extra Repayments Calculator Australia

What the three strategies do

An ordinary savings account earns interest, which is generally taxable. A mortgage offset account does not usually pay savings interest; instead, its balance reduces the loan amount charged interest. Extra repayments reduce the loan principal directly. All three can improve a household balance sheet, but they differ in fees, access and behavioural risk.

Why offset savings are not identical to a savings rate

Saving mortgage interest produces a return linked to the home-loan rate. For an owner-occupied loan, that interest saving is not ordinary bank interest paid to you. A separate savings account may need a higher advertised rate to deliver the same after-tax benefit.

An offset is not automatically better. Some offset-eligible loans charge package fees or a higher interest rate. A low average offset balance can fail to recover those costs.

Extra repayments and redraw

Paying cash directly into the loan normally reduces principal immediately. A redraw facility may allow some extra repayments to be withdrawn later, but the lender’s access rules, limits and fees apply. Redraw should not be described as identical to cash in a transaction account.

How the model works

The calculator keeps the scheduled repayment based on the chosen loan and applies the cash strategy month by month. Offset interest is calculated after reducing the chargeable balance by the eligible offset amount. The extra-repayment scenario applies the starting cash to principal and adds monthly extra repayments.

The savings scenario grows the cash at the entered interest rate after the estimated marginal tax rate. It keeps the mortgage unchanged so you can see the trade-off between accessible savings and loan interest.

Decision checks

• Compare the loan rate and fee with a similar no-offset product.
• Use an average offset balance, not the highest balance seen on payday.
• Confirm whether the offset is 100% or partial.
• Check redraw access, minimum amounts and lender discretion.
• Keep emergency money accessible enough for your circumstances.

What the three scenarios actually compare

The ordinary-savings scenario leaves the mortgage unchanged and grows the cash account using the entered savings rate after estimated tax on interest. The offset scenario keeps the cash accessible while reducing the balance used to calculate mortgage interest. The extra-repayment scenario permanently reduces the loan balance unless the product provides redraw access.

All three scenarios use the same starting cash and monthly contribution. This prevents a common comparison error where the offset is credited with savings deposits that are not included in the extra-repayment case.

Why an offset can outperform a savings account

Mortgage interest saved through a genuine offset is not savings-account interest paid to the borrower. It reduces interest charged on the home loan, so there is generally no separate interest income to include in taxable income. By contrast, interest earned in an ordinary savings account is generally taxable.

If the mortgage rate is 6% and a savings account pays 5%, the offset can still have the stronger after-tax effect. However, the offset loan may charge a higher rate or annual package fee. Those costs must be deducted before calling the offset worthwhile.

Offset and extra repayments can have similar interest effects

When rates and timing are identical, one dollar in a 100% offset can reduce interest by roughly the same amount as one dollar paid directly against the loan. The difference is access and account structure. Offset money remains in a separate transaction account. Extra repayments reduce the loan and may only be accessible through redraw under the lender’s rules.

This distinction can matter for emergencies, investment use, relationship changes and tax tracing. The calculator measures interest and accessible cash; it does not determine the legal or tax consequences of moving money through redraw.

Calculate the offset break-even balance

An offset is worth its extra annual cost only when interest savings exceed the package fee and any rate premium. A rough break-even average balance is annual extra cost ÷ mortgage rate. For example, $395 of extra annual cost at 6% requires an average balance of about $6,583 before considering timing and compounding.

If the offset product is 0.10 percentage points more expensive on a $500,000 loan, that rate premium adds roughly $500 in first-year interest before principal changes. Add it to the annual fee when estimating the balance required.

Use average balance, not the payday peak

Home-loan interest is commonly calculated daily. A salary that enters the offset and is spent over the month produces a lower average balance than the amount visible on payday. Enter the amount that is likely to remain on average and the actual monthly contribution after spending.

For households using a credit card for expenses, the strategy only works when the card is cleared in full and fees or interest do not exceed the mortgage saving. The calculator does not assume credit-card use.

Three tests before choosing

1. Low-balance case: reduce the starting cash and monthly deposits to see whether fees erase the offset benefit.
2. Liquidity case: decide how much cash must remain immediately accessible.
3. Discipline case: test whether redraw or offset access makes it more likely the money will be spent.

The mathematical winner is not always the behavioural winner. Direct repayments can be stronger for someone who would repeatedly spend an offset balance, while an offset can be valuable for someone who needs a large emergency reserve.

Tax and ownership limitations

Tax outcomes can differ when a home later becomes an investment property or when redraw funds are used for mixed purposes. Account ownership and loan purpose also matter. The calculator uses a simple marginal tax rate for savings interest and does not trace deductible debt. Seek tax advice before restructuring a loan for investment purposes.

Official sources and review notes

This calculator is general information. The calculations use the assumptions shown on the page and do not determine legal status, eligibility, tax outcomes, lending approval or financial-product suitability.

• Moneysmart — Mortgage offset accounts — How offset accounts work, fees, access and redraw differences.
• Moneysmart — Pay off your mortgage faster — Official guidance on extra repayments and loan features.

Related calculators and guides

• Everyday Money CalculatorsBrowse related Australian decision tools.
• Offset Account vs Extra Repayments: Which Saves More?Compare mortgage interest savings, access to cash, fees and payoff time for offset accounts and extra repayments.
• Is an Offset Account Worth the Annual Fee?Calculate the average offset balance needed to recover package fees and any higher loan rate.
• Why Mortgage Interest Savings Can Beat Taxable Savings InterestCompare the effective benefit of reducing owner-occupied mortgage interest with earning interest in a bank account.
• Redraw vs Offset Account in Australia: Key DifferencesUnderstand access, control, tax records, fees and interest effects before choosing redraw or an offset account.
• How Regular Offset Deposits Change a Home LoanSee how salary deposits and monthly savings can reduce interest and shorten a mortgage over time.

Frequently asked questions