Extra Repayments, Offset & Redraw
What if you could pay off your home loan years earlier without changing your lifestyle? Extra repayments, offset accounts and redraw facilities are the three most powerful tools for destroying debt faster than the bank planned. Calculate exactly how much time and money each strategy saves — and discover why the banks do not advertise these benefits.
Practise this lesson
Three printable worksheets that build from foundations to mastery — or build your own from any module’s questions.
A $400,000 loan at 5% p.a. over 30 years has a minimum monthly repayment of $2,147. The borrower pays $2,500 every month instead — an extra $353.
Without calculating — do you think this small extra payment saves: (a) less than 1 year, (b) 2–5 years, or (c) more than 5 years? Predict before you learn.
Key facts
- How extra repayments reduce loan term and total interest
- How offset accounts work mathematically
- The difference between offset accounts and redraw facilities
Concepts
- Why early extra payments save more than late extra payments
- The opportunity cost of money in offset vs other investments
- Why banks prefer minimum repayments
Skills
- Calculate years and interest saved with extra repayments
- Compare offset account benefits against savings accounts
- Evaluate redraw vs offset for different scenarios
- Build a debt-reduction strategy
Every dollar above the minimum repayment goes straight to principal. Because interest is calculated on the remaining balance, reducing principal early has a compounding effect that accelerates over time.
$P$ = principal, $r$ = monthly rate, $M_{\text{new}}$ = new (higher) monthly payment, $n$ = number of months remaining
Interest saved compared to minimum repayments:
Example — $400,000 at 5% p.a. (min $2,147/month):
| Monthly payment | Term | Total interest | Interest saved |
|---|---|---|---|
| $2,147 (minimum) | 30 years | $373,000 | — |
| $2,500 | 22.5 years | $257,000 | $116,000 |
| $3,000 | 17.5 years | $185,000 | $188,000 |
| $3,500 | 14.5 years | $145,000 | $228,000 |
An extra $353/month saves 7.5 years and $116,000. That is a 111% return on the extra money invested over the life of the loan.
Extra repayments reduce principal — reducing the balance on which compound interest grows; Formula: $n_{\text{new}} = \dfrac{-\ln(1 - Pr/M_{\text{new}})}{\ln(1+r)}$ to find the new term
Pause — copy the new-term formula $n_{\text{new}} = \dfrac{-\ln(1 - Pr/M_{\text{new}})}{\ln(1+r)}$ and the principle (extra repayments hit principal directly, not interest) into your book.
Quick check: A borrower pays $500 extra per month on their mortgage. Where does this extra $500 go?
Worked examples · offset & extra repayments
A $500,000 loan at 5.2% p.a. has a minimum repayment of $2,748/month. The borrower pays $3,200/month. How many months until the loan is paid off?
A $300,000 loan at 4.8% p.a. has a minimum repayment of $1,573/month. The borrower has $40,000 in an offset account. Find: (a) the effective balance, (b) the new minimum repayment, (c) interest saved in the first month.
Did you get this? True or false: keeping $50,000 in an offset account on a 5% loan earns the same as a savings account paying 5% interest (taxed at 32.5%).
We just saw that paying $353 extra per month can save 7.5 years and $116,000 in interest — because extra money hits principal directly. That raises a question: banks offer two structures for parking spare cash — offset accounts and redraw facilities — which strategy wins and why? This card answers it → comparing the tax-free interest-saving rate of offset against redraw's locked-in approach.
Both offset and redraw reduce the balance on which interest is calculated. The difference is accessibility and tax treatment.
| Feature | Offset account | Redraw facility |
|---|---|---|
| Accessibility | Instant (ATM, card, BPAY) | Request required — takes 1–3 days |
| Tax treatment | Not taxable (you're saving, not earning) | Same — not taxable |
| Fees | Often an annual account fee (~$300–$400) | Usually free or low cost |
| Best for | Daily transaction account / emergency fund | Lump-sum extra repayments |
| Risk | Lender can freeze access if you default | Same — lender controls |
Offset & redraw both reduce effective principal — but neither permanently reduces the stated loan balance; Both are reversible: offset money can be withdrawn; redraw money can be re-accessed by request
Pause — copy the offset interest formula $\text{Interest} = (P - \text{offset}) \times r$ and the key comparison (offset: instant access, fees apply; redraw: locked until requested, usually free) into your book.
Fill in the blank: An offset account reduces the balance on which ___ is calculated. The mathematical effect is: Interest $= (P - \_\_\_) \times r$.
Common errors · the 3 traps that cost marks
Match each feature to the correct product:
Quick-fire practice · 4 calculations
A $400,000 loan at 5% p.a. monthly. Extra $300/month above minimum ($2,148). Estimate (or calculate) the years saved.
Same loan — extra $500/month. Total interest saved vs minimum?
A $400,000 loan at 5%. Offset of $50,000. What is the effective balance, and what is the monthly interest saving?
Is keeping $50,000 in offset better than a savings account at 4% p.a. taxed at 32.5%? Show your comparison.
Did you get this? True or false: extra repayments made in the first year of a mortgage save more total interest than the same extra repayments made in the final year.
Earlier you predicted whether an extra $353/month would save less than 1, 2–5, or more than 5 years. The answer: paying $2,500 instead of $2,147 on a $400,000 loan at 5% pays off the loan in approximately 22.5 years — saving 7.5 years. Total interest drops from $373,000 to $257,000, a saving of $116,000.
An extra $4,236/year saves $116,000 over the loan life. The return is extraordinary because every extra dollar attacks the principal when the balance — and therefore the compounding — is at its highest.
Pick your answer, then rate your confidence — that tells the system what to drill next. Each retry pulls a fresh mix.
Q1. A $300,000 loan at 5.4% p.a. compounded monthly has a minimum repayment of $1,687/month. The borrower pays $2,000/month. (a) Find the new loan term in months using $n = \dfrac{-\ln(1 - Pr/M)}{\ln(1+r)}$. (b) How many years does this save? (3 marks)
Q2. A $450,000 loan at 5% p.a. has a minimum repayment of $2,414/month. The borrower holds $60,000 in an offset account. (a) Find the effective loan balance. (b) Calculate the monthly interest saving. (c) Is this better than a savings account at 4% p.a. taxed at 32.5%? Show working. (3 marks)
Q3. A borrower has $350,000 outstanding at 4.5% p.a. and $30,000 to allocate to debt reduction. Compare the mathematical effect of: (a) placing $30,000 in an offset account, and (b) making a single $30,000 lump-sum extra repayment. Which strategy is more flexible and why? (4 marks)
Comprehensive answers (click to reveal)
Drill answers:
1. Extra $300: new monthly = $2,448. $n = -\ln(1 - 400{,}000 \times 0.004167 / 2{,}448) / \ln(1.004167) \approx 288$ months = 24 years. Saves 6 years.
2. Extra $500: new monthly = $2,648. $n \approx 246$ months = 20.5 years. Interest = $2,648 \times 246 = \$651{,}408$. Minimum total = $2,148 \times 360 = \$773{,}280$. Saved $\approx \$121{,}872 \approx \$135{,}000$ (table-rounded).
3. Effective balance $= \$350{,}000$. Monthly saving $= 50{,}000 \times 0.004167 = \$208.35/\text{month}$.
4. Offset: 5% guaranteed, tax-free. Savings: $4\% \times (1 - 0.325) = 2.7\%$. Offset is superior by 2.3 percentage points.
Q1 (3 marks): $r = 0.054/12 = 0.0045$ [1]. $n = -\ln(1 - 300{,}000 \times 0.0045/2{,}000)/\ln(1.0045) = 199$ months $\approx 16.6$ years [2]. Saves $30 - 16.6 = 13.4$ years [1].
Q2 (3 marks): (a) Effective $= 450{,}000 - 60{,}000 = \$390{,}000$ [1]. (b) Saved $= 60{,}000 \times (0.05/12) = \$250$/month [1]. (c) After-tax savings $= 4\% \times 0.675 = 2.7\%$. Offset earns 5%, so offset is far better [1].
Q3 (4 marks): Both reduce interest by the same monthly amount: $30{,}000 \times 0.045/12 = \$112.50$/month [1]. Offset: $350{,}000 \to \$320{,}000$ effective. Same saving as lump sum [1]. Difference: offset money is accessible instantly; lump sum goes into loan permanently (recoverable via redraw only if facility exists) [1]. Offset is more flexible for emergencies but may carry an annual fee [1].
Five timed questions on extra repayments, offset maths and redraw. Beat the boss to bank a tier — gold (90% + speed), silver (75%), bronze (50%). Replays welcome.
⚔ Enter the arenaClimb platforms using extra repayment impact, offset mathematics and redraw strategies. Pool: lessons 1–15.
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