How Offset Accounts Save You Money — With Examples (2026)
An offset account reduces the loan balance on which interest is charged — dollar for dollar. The savings can be substantial, especially for borrowers who keep significant funds in offset. Here are the worked examples to show exactly how it works.
The Core Mechanism
Interest on an Australian mortgage is typically calculated daily on the outstanding principal balance.
With an offset account:
$$\text{Interest charged} = (\text{Loan balance} - \text{Offset balance}) \times \frac{\text{Annual rate}}{365}$$
The offset account balance is subtracted before interest is calculated — not after. Every dollar in the offset account saves you one day’s worth of interest on that dollar, every day it sits there.
Example 1: $600,000 Loan, $30,000 in Offset
Loan details: $600,000 outstanding balance at 6.00% p.a.
| Without offset | With $30,000 in offset |
|---|---|
| Interest on $600,000 | Interest on $570,000 |
| $3,000/month | $2,850/month |
| Saving: $150/month = $1,800/year |
Over a 25-year remaining term with constant offset balance: approximately $24,000 in total interest saved.
Example 2: $700,000 Loan, $50,000 in Offset
Loan details: $700,000 outstanding balance at 6.00% p.a.
| Without offset | With $50,000 in offset |
|---|---|
| Interest on $700,000 | Interest on $650,000 |
| $3,500/month | $3,250/month |
| Saving: $250/month = $3,000/year |
Example 3: Salary Cycling Through the Offset
The maximum benefit from an offset account comes when you use it as your everyday transaction account — your salary deposits and sits in offset for weeks before bills leave.
Scenario: $600,000 loan at 6%. You earn $8,000/month (net). Your bills total $5,000/month, leaving $3,000 building as savings.
Average offset balance over time (assuming salary arrives Day 1, bills spread across the month):
- Year 1 average: ~$15,000 in offset
- Year 2 average: ~$28,000 in offset (savings accumulating)
- Year 3 average: ~$42,000 in offset
Interest saving in Year 3 alone: $42,000 × 6% = $2,520
The compounding effect: as your savings grow (kept in offset rather than a separate account), your interest saving grows proportionally.
The Tax Advantage of Offset
Interest savings through an offset account are not taxable income — unlike interest earned in a savings account.
Comparison for a borrower in the 37% tax bracket:
| Strategy | Gross return | Tax | Net benefit |
|---|---|---|---|
| Savings account at 5.5% | 5.5% | 37% tax = 2.0% | 3.5% net |
| Offset account at 6% loan rate | 6.0% | Tax-free | 6.0% net |
The offset account delivers the equivalent of a 6% after-tax return on your savings — consistently beating most savings accounts on an after-tax basis.
For borrowers in the 45% top marginal tax bracket, this advantage is even greater.
How the Loan Term Is Affected
If you maintain a substantial, growing offset balance, you effectively accelerate the repayment of your loan even though your minimum repayment stays the same. More of each payment goes to principal (because less interest accrued), and the loan term shortens.
$600,000 at 6%, $40,000 constant offset balance:
- Monthly interest saving: ~$200
- Over 30 years: ~$45,000 in interest saved
- Estimated term reduction: ~2 years
This assumes a static $40,000 — a growing offset balance would save more.
The Optimal Offset Strategy
Use your offset account as your primary transaction account:
- Salary is deposited into the offset account on pay day
- Bills, mortgage repayments, and spending are paid from the offset
- Savings accumulate in the offset rather than a separate savings account
- The offset balance fluctuates, but is always working to reduce daily interest
This “salary cycling” approach maximises the time each dollar spends in the offset account before it is spent — extracting maximum interest savings.
Does Offset Work on Fixed Rate Loans?
Generally, offset accounts are only available on variable rate loans. Some lenders offer offset accounts on fixed rate loans, but these are less common and the feature may be partial (e.g., capped at a certain balance).
A common strategy is a split loan — fixing part for rate certainty and leaving part variable with offset attached.
→ See Split Loan Strategy
Frequently Asked Questions
What if I only have a small amount in offset — is it still worth it?
Yes — every dollar saves interest. The break-even question is whether the annual fee (if your loan has one) is justified by your offset balance. At 6%, a $395 annual fee is offset by approximately $6,600 in the account. Any balance above that is pure saving.
Is a high-interest savings account ever better than an offset account?
For borrowers in the top 45% marginal tax bracket: a savings account would need to return approximately 10.9% gross to match a 6% offset account’s after-tax benefit. No mainstream savings account comes close to this. For lower-rate borrowers or those on lower tax brackets, the comparison is closer — but offset is usually still superior if the loan rate exceeds the after-tax savings rate.
How often is offset calculated?
Most major Australian lenders calculate offset daily and apply it to the daily interest accrual. Confirm this with your lender — some older-style loans may calculate monthly.
Related Guides
- What Is a Mortgage Offset Account?
- 100% Offset vs Partial Offset
- Offset Account vs Extra Repayments
- Offset Account vs Term Deposit
- Mortgage Repayment Hub
Worked examples are estimates based on a constant interest rate and offset balance. Actual savings will vary with rate changes, fluctuating offset balances, and lender-specific calculation methods. Tax treatment of offset accounts for investment properties is complex — speak with a registered tax agent. For advice tailored to your situation, speak with a licensed mortgage broker. Find one through MoneySmart.