Personal finance / Evergreen
An offset balance is not the same as repaying the mortgage
An Australian account feature changes interest calculations while access and pricing still matter.
Separate an offset account balance, mortgage principal, and redraw access when comparing loan features.
Follow the two balances
A fictional Australian borrower has a mortgage balance of A$400,000 and A$20,000 in a linked full offset account. In the simplified calculation, interest is based on A$380,000. The borrower still owes A$400,000 of principal; the deposit and loan remain separate balances. ASIC's Moneysmart explains that an offset account can reduce mortgage interest when correctly linked. Calling the deposit a mortgage repayment obscures what happened. The account changes the balance used to calculate interest without necessarily making an extra payment to extinguish the debt.
Estimate one year's gross effect
Assume, only for teaching, a constant 6% annual mortgage rate, a constant A$20,000 offset balance, and a full-year simple approximation. The gross interest difference is A$20,000 × 6% = A$1,200. Actual lenders may calculate interest daily, while balances and rates can change. This A$1,200 is interest avoided under the assumptions, not interest paid into the deposit account and not a guaranteed investment return. If money leaves the offset halfway through the year, a full-year estimate overstates the effect of that portion.
Compare the feature's incremental cost
Suppose a fictional offset-enabled loan adds A$360 in annual package charges compared with an otherwise equivalent option. The simplified net difference is A$1,200 − A$360 = A$840 before any rate difference or other costs. If maintaining the feature also means paying a higher mortgage rate, that difference must be applied to the relevant loan balance. A small rate increase on a large loan can absorb the saving from a smaller offset deposit. Do not compare the offset's benefit with zero while ignoring the actual alternative contract.
Do not confuse offset with redraw
Moneysmart distinguishes cash held in an offset account from access to additional repayments through a redraw facility. Availability, conditions, charges, and lender discretion can differ. A label in an app is not enough to establish that cash will be available when needed. Read the actual terms and verify the linkage. Tax consequences can also differ according to how borrowed funds are used; this example does not resolve deductibility. A borrower planning to change a property's use needs qualified local advice rather than a general claim that the two arrangements are interchangeable.
Run a balance sensitivity exercise
Recalculate the fictional gross effect with average offset balances of A$5,000, A$10,000, and A$20,000 at the same assumed 6%. The results are A$300, A$600, and A$1,200 before feature costs. Subtract the same A$360 charge from each, then write what remains unknown about rates and access. This makes the decision depend on realistic balances rather than a promotional maximum. Outside Australia, verify whether the local product works the same way. Continue with the paycheck lesson to distinguish money available for bills from cash already committed elsewhere.
A global perspective
Original financial education with hypothetical examples; no personalized investment, tax, or legal advice. The named country is the example jurisdiction, not a proxy for its continent. International-framework articles name that scope explicitly.
Sources & further reading
ASIC Moneysmart — Mortgage offset accounts ↗Sources checked Oct 18, 2026. Examples are original illustrations. No affiliation with cited organizations.
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What assumption in this guide would change the result in a different situation? Revisit the example and explain that change in your own words.
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