An offset account is one of the most powerful tools in the Australian mortgage market — and one of the most misunderstood. Many borrowers have one attached to their home loan and don't realise how it's actually saving them money, or how to maximise it. This guide explains the mechanics clearly, with real numbers.
An offset account is a transaction account linked to your home loan. The balance in the account is "offset" against your loan balance when the bank calculates your interest each day. You don't earn interest on the offset account — instead, you pay less interest on your mortgage.
Here's why that matters: mortgage interest in Australia is typically 6–7%. The interest you'd earn on a savings account is typically 4–5%. So $50,000 in an offset account saves you 6.5% in mortgage interest — effectively earning you 6.5% on those funds, tax-free (unlike savings account interest, which is taxed at your marginal rate).
At 6.19% interest rate, the daily interest charge drops from $101.73 to $93.25 — saving $8.48 every single day, or $3,095/year.
Australian mortgages calculate interest daily based on the closing balance each day. This is why the timing of your salary deposit matters — the moment your pay hits your offset account, that amount starts reducing your interest charge.
The formula is simple:
Daily interest = (Loan balance − Offset balance) × Annual rate ÷ 365
Your monthly repayment stays fixed. But with a smaller effective balance, less of each repayment goes to interest — so more goes to principal. This is why your loan gets paid off faster even though you're making the same repayment amount.
| Offset balance | Annual interest saving | Time saved | Total interest saved |
|---|---|---|---|
| $0 (no offset) | — | — | — |
| $20,000 | $1,238/yr | ~11 months | ~$35,000 |
| $50,000 | $3,095/yr | ~2.5 years | ~$87,400 |
| $100,000 | $6,190/yr | ~5.2 years | ~$172,000 |
| $150,000 | $9,285/yr | ~8.5 years | ~$246,000 |
Every dollar in your offset account saves you your mortgage interest rate in guaranteed, tax-free return. At 6.19%, $1 in offset saves $0.0619 per year — better than most savings accounts after tax, with zero risk and full accessibility.
Both offset and redraw reduce the interest on your loan, but there are important practical differences:
| Offset account | Redraw facility | |
|---|---|---|
| Your money | Sits in a separate account | Sits inside the loan |
| Access | Instant — it's your transaction account | Usually accessible but lender controls it |
| Interest saving | Daily, on full balance | Daily, on full balance |
| Tax treatment | No interest earned = no tax | No interest earned = no tax |
| Investment property | ✅ Use offset — keeps loans clean | ❌ Redraw can contaminate deductibility |
| Cost | Usually $10–15/month on loan | Usually free |
For investment properties, offset is significantly better than redraw. If you redraw funds from an investment loan for personal use (a holiday, car, etc.), the interest on that portion may no longer be tax-deductible. Offset keeps the loan "clean" because the money never enters the loan.
Because interest is calculated daily, every day your salary sits in the offset account is a day you're not paying interest on that amount. A simple strategy used by many mortgage holders:
If you have $5,000 in salary sitting in your offset for an average of 15 days each month before spending it, that saves roughly $760/year on a 6.19% loan — for zero effort. Over 30 years of the loan, that compounds to thousands more in savings.
Offset accounts are most valuable when:
If you have very little savings and tight cash flow, extra repayments (direct to the loan) or a redraw facility may be simpler and equally effective without the account fee.
Paying fortnightly rather than monthly is often confused with the offset effect — but it's a separate strategy. Here's why fortnightly payments genuinely save money:
There are 26 fortnights in a year, but only 12 months. If your monthly repayment is $3,000, your annual repayment is $36,000. Paying half fortnightly ($1,500 × 26) means you pay $39,000/year — an extra $3,000 annually that goes straight to principal. On a $600,000 loan at 6.19%, this saves roughly $75,000 in interest and cuts 4–5 years off the loan term.
Enter your loan details, offset balance, and any extra repayments to calculate precisely how much you'd save — including a year-by-year amortisation table.
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