A mortgage offset account is a transactional bank account linked to a home loan where the balance in the offset account is used to reduce the principal on which interest is calculated. If you have a $500,000 home loan and $100,000 sitting in a 100% offset account, the bank calculates interest as though the loan balance were $400,000 — saving you interest on the offset amount at the same rate as your mortgage. Unlike making extra repayments, the money in the offset account remains fully accessible: you can withdraw it at any time, making offset accounts one of the most powerful tools for managing both debt and liquidity simultaneously. A 100% offset account offsets the full amount of the linked deposit, dollar for dollar, against the loan balance. Some lenders offer partial offset accounts that only offset a portion of the deposit (e.g., 40%), which are less effective. Interest savings in an offset account are equivalent to earning the loan interest rate on the offset balance — and those savings are tax-free for owner-occupier borrowers, unlike interest earned in a regular savings account which is assessable income. This makes offset accounts particularly effective for high-income borrowers in higher tax brackets. The difference between an offset account and a redraw facility is critical: a redraw facility requires extra repayments to be made first, and then redrawn if needed — withdrawing from a redraw facility reduces your ability to claim interest deductions on a mixed-purpose loan. With an offset account, the money is never contributed to the loan, preserving deductibility if the loan purpose later changes. Many borrowers keep multiple offset accounts for different savings goals — emergency fund, holiday savings, renovation budget — all linked to one loan, each reducing interest.
Daily Interest = (Loan Balance - Offset Balance) × Annual Interest Rate / 365; Monthly Interest Saving = Offset Balance × Annual Rate / 12; Interest Saving Per Year = Offset Balance × Loan Interest Rate
- 1Link the offset account to your home loan — most variable rate loans and some fixed loans offer this feature.
- 2Deposit your salary and any savings into the offset account rather than a separate bank account.
- 3The bank calculates your daily interest on the net loan balance (loan outstanding minus offset balance) every day.
- 4Interest charges each month are reduced by the amount equivalent to the offset balance multiplied by the daily interest rate.
- 5Your required minimum repayments remain the same, but a greater portion of each repayment reduces principal (since less is consumed by interest).
- 6The loan is paid off faster without making any additional formal contributions — simply by keeping money in the offset.
- 7Withdraw money from the offset as needed for living expenses, emergencies, or purchases — the offset balance adjusts daily.
Interest is charged on $400,000 not $500,000 — saving $6,000/year at no cost
Offset balance $100,000 × 6% = $6,000 annual interest saving. No tax payable on this saving (unlike a savings account).
Offset account is equivalent to earning 6% with no tax — superior to a 5.5% savings account at 37% marginal rate
Offset: $80,000 × 6% = $4,800 saving (tax-free). Savings: $80,000 × 5.5% × 63% after tax = $2,772. Offset better by $2,028/year.
Average offset balance over month (salary arrives, expenses drawn down) drives the daily interest saving
Average $15,000 offset × 6% = $900/year saving. Over 25-year term this accelerates payoff and saves significant total interest.
Many lenders allow 1-10 offset accounts; all balances aggregate to reduce the loan
$63,000 × 6% = $3,780/year saving across all three accounts combined.
A homeowner depositing their salary into a mortgage offset account to reduce daily interest and pay off their loan years earlier.. This application is commonly used by professionals who need precise quantitative analysis to support decision-making, budgeting, and strategic planning in their respective fields
A high-income earner comparing the after-tax return from an offset account versus a term deposit to determine where to park surplus cash.. Industry practitioners rely on this calculation to benchmark performance, compare alternatives, and ensure compliance with established standards and regulatory requirements
A property investor deciding whether to use an offset account or a redraw facility on their investment loan, considering deductibility implications.. Academic researchers and students use this computation to validate theoretical models, complete coursework assignments, and develop deeper understanding of the underlying mathematical principles
A couple using multiple linked offset accounts to separately track holiday savings, emergency fund, and renovation savings while all reducing mortgage interest.. Financial analysts and planners incorporate this calculation into their workflow to produce accurate forecasts, evaluate risk scenarios, and present data-driven recommendations to stakeholders
A mortgage broker showing a client how much faster their home loan is repaid with a full salary offset versus a standard principal and interest loan.. This application is commonly used by professionals who need precise quantitative analysis to support decision-making, budgeting, and strategic planning in their respective fields
Investment Property and the Offset
For investment properties, an offset account reduces the deductible interest expense. While the cash saving is real, the reduced deduction increases taxable income. High-income investors should model whether the after-tax savings from an offset on an investment loan outweigh the reduction in tax deductions.
Contamination Risk on Mixed Loans
If you use a redraw on a home loan to fund a private expense and later convert the property to an investment, the private redraw portion contaminates the loan — that portion's interest is not deductible. An offset account avoids this because funds never enter the loan, preserving the original loan purpose and full deductibility.
Fixed Rate Offset Restrictions
Most fixed rate home loans do not offer a 100% offset account. Some lenders offer a partial offset on fixed loans. If your loan is fully fixed, consider keeping surplus funds in a high-interest savings account until the fixed period ends, then establishing a proper offset account.
Bridging Loans and Offset
Bridging loans (used to buy a new property before selling the existing one) often have offset account functionality. The proceeds from the old property sale sit in the offset, dramatically reducing the peak interest during the bridging period, which can be at high short-term rates.
| Offset Balance | Loan Rate 6% | Annual Interest Saving | After-Tax Equivalent Savings Rate (37% tax) |
|---|---|---|---|
| $20,000 | 6% | $1,200 | 9.52% |
| $50,000 | 6% | $3,000 | 9.52% |
| $100,000 | 6% | $6,000 | 9.52% |
| $200,000 | 6% | $12,000 | 9.52% |
| $500,000 | 6% | $30,000 | 9.52% |
What is the difference between an offset account and a redraw facility?
A redraw facility allows you to redraw extra repayments you have already made to the loan. An offset account is a separate transaction account — money never enters the loan. For investment properties, keeping funds in an offset (rather than redrawing) preserves the loan's investment purpose, protecting interest deductibility if use changes.
Are offset savings taxable?
No. The interest saving from an offset account is not assessable income — you are simply paying less interest, not earning investment income. This is a significant advantage over savings accounts where interest earned is taxable at your marginal rate. This is an important consideration when working with australia offset account calculations in practical applications. The answer depends on the specific input values and the context in which the calculation is being applied.
Do all home loans offer offset accounts?
No. Offset accounts are typically available on variable rate home loans. Some fixed rate loans do not offer offset functionality, or offer a partial offset only. Basic (no-frills) variable rate loans may also not include an offset account, though they may offer lower interest rates to compensate. This is an important consideration when working with australia offset account calculations in practical applications.
Can offset accounts be used on investment loans?
Yes, but careful management is required. An offset account on an investment loan reduces the deductible interest — the interest saving is a cash benefit, but the loan interest deduction is also reduced. For most investors, a redraw on investment loans may be more complex than an offset account for ongoing tax deductibility management.
Does the offset account earn interest?
No. Offset accounts do not earn interest — instead, the balance is used to reduce the interest charged on the linked loan. The effective return is the same as the loan interest rate, which is typically higher than deposit savings rates, making it financially superior in most market conditions. This is an important consideration when working with australia offset account calculations in practical applications.
Can I have multiple offset accounts on one loan?
Yes, many lenders allow multiple offset accounts (sometimes up to 10) linked to a single loan. All balances are aggregated when calculating the daily interest on the loan. This allows you to compartmentalise savings for different goals while all benefiting from the offset effect. This is an important consideration when working with australia offset account calculations in practical applications. The answer depends on the specific input values and the context in which the calculation is being applied.
What happens to the offset balance if I switch lenders?
If you refinance to a new lender, you simply move your offset account funds to the new offset account. There is no loss of funds — unlike a redraw facility where the process can be more complicated. Your offset account balance is always accessible and can be transferred on refinancing.
Is the deposit in an offset account government-guaranteed?
Yes. Deposits in an offset account are protected by the Australian Government's Financial Claims Scheme (FCS) up to $250,000 per account holder per ADI (Authorised Deposit-taking Institution). This is the same protection as a standard bank deposit. This is an important consideration when working with australia offset account calculations in practical applications. The answer depends on the specific input values and the context in which the calculation is being applied.
Pro Tip
If you have surplus funds sitting in a savings account earning taxable interest, consider moving them to your mortgage offset account instead. At a 6% mortgage rate and 37% marginal tax rate, your effective return in an offset account is equivalent to earning 9.52% in a savings account.
Did you know?
Offset accounts are relatively unique to Australia, New Zealand, and the UK. The concept was pioneered in Australia in the early 1990s and has become a standard feature of Australian home lending, with millions of Australians now using offset accounts as their primary savings vehicle.