Property values and interest rates move independently, and your investment loan feels both. Understanding how each one changes your repayments and your borrowing position helps you make steady decisions instead of reactive ones.
This guide is for Hills District investors who already own, or are planning to buy, a rental property. Whether you are in Castle Hill, Baulkham Hills, Kellyville or nearby, the same principles apply. We want you to feel informed and in control, whatever the market does next.
How Do Interest Rate Changes Affect Investment Loan Repayments?
A rise in your interest rate increases repayments on a variable rate loan straight away, and the size of the rise depends on your loan amount and repayment type. A fixed rate holds your repayments steady until the fixed term ends, then the loan usually reverts to the lender's variable revert rate unless you refix or refinance.
Here is an illustrative example using a rate of 6.75% p.a. Say an investor has a $600,000 interest-only loan. The monthly interest is about $3,375. If the variable rate rises by 0.5 percentage points to 7.25%, the monthly interest becomes about $3,625. That is $250 more each month, or $3,000 over a year, which the rent needs to absorb or the investor needs to fund.
This is why calculating investment loan repayments at a few different rates is a healthy habit. Our calculators let you test a higher rate before it arrives.
The trade-off with fixing is that you give up flexibility. Depending on the lender, a fixed loan may limit extra repayments, and leaving early can trigger break costs. Ask about these before you choose.
What Happens to Your LVR When Property Values Change?
Your loan to value ratio (LVR) is your loan divided by your property's value, so it falls when values rise and climbs when they fall. Lenders use it to decide how much more you can borrow and whether Lenders Mortgage Insurance (LMI) applies.
Using the same $600,000 loan, suppose the loan sits at exactly 80% of the property's value. If a valuation comes in 10% lower, the LVR rises to about 88.9%. If it comes in 10% higher, the LVR drops to about 72.7%.
The 80% mark matters because LMI is generally required above it. It is not a legal borrowing limit. Each lender sets its own caps and policies, so the outcome depends on who you borrow from.
The risk of a falling valuation is practical. A higher LVR can limit your options if you want to refinance, buy again or release equity. It does not change your repayments on its own, as long as you keep meeting them.
Interest Only or Principal and Interest When Rates Move?
Interest only keeps repayments lower in the short term, while principal and interest reduces your debt over time. Neither is right for everyone, and the choice affects how exposed you are to rate rises.
Using the same illustrative 6.75% rate on a $600,000 loan over 30 years, principal and interest repayments are about $3,892 a month. If the loan is interest only for five years, the repayment is about $3,375 a month. After that, it reverts to principal and interest over the remaining 25 years, which lifts the repayment to about $4,146 a month. You need to be ready for that step up.
An interest-only loan does not increase how much you can borrow. Under APRA's guidance, lenders assess you on principal and interest repayments over the remaining term after the interest-only period. APRA also requires ADIs to assess new borrowers at a rate at least 3 percentage points above the loan rate. This is an assessment at application, and it does not limit how far your actual rate can rise. Non-bank lenders are not subject to it. Test your own repayments at higher rates.
On tax, interest on money borrowed to buy or hold a rental property is generally deductible, while the principal part of a repayment is not. Because tax rules for investors have changed, including the treatment of losses on established properties bought after 12 May 2026, speak with your accountant about your situation. A tax outcome is never certain.
Using Rising Property Values: Equity Release With Care
If your property value grows, you may be able to release equity to fund a deposit on another purchase, subject to lender policy and your ability to repay. The extra borrowing also adds repayments, so it increases your exposure to rate rises.
How you use the money matters for tax. Interest is generally deductible only to the extent the borrowed funds are used to produce income. Money drawn from an investment loan for private purposes does not carry deductible interest, even though the property is the security. Your accountant can confirm how this applies to you.
Leverage can help build wealth over time, but it also magnifies losses if values fall or rates rise. A buffer in an offset account can soften that pressure. An offset reduces the interest charged, but it does not reduce the loan balance when lenders measure your LVR.
Is It Time to Refinance Your Investment Loan?
Refinancing is worth considering when your rate has drifted above what other lenders offer, your fixed term is ending, or your LVR has improved. The rate you pay on an investment loan depends on your deposit size, loan structure and lender, and rate discounts vary between lenders.
A rising property value can strengthen your position, as a lower LVR may open up more lender choices. Costs such as discharge or valuation fees can apply, so weigh these against any saving. If a fixed term is about to end, our fixed rate expiry page explains your choices, and our refinancing team can compare lenders on our panel on your behalf.
A loan health check is a sensible starting point if you are unsure where your current loan stands. If you are planning your next purchase, we can also estimate your borrowing capacity and talk through suitable investment loans for your goals.
Property and rates will keep changing. A clear plan, honest numbers and a buffer you are comfortable with are what keep your investment on course.
Call one of our team or book an appointment at a time that works for you. We will go through your numbers with you, explain your options plainly and help you plan for both rising rates and shifting values.
Frequently Asked Questions
How much more will I pay if my investment loan rate rises 0.5%?
On an illustrative $600,000 interest-only loan, a rise from 6.75% to 7.25% adds about $250 a month. The exact amount depends on your loan size and repayment type.
What happens to my LVR if my property value falls?
Your LVR rises, because the loan stays the same while the value drops. If a loan at 80% LVR sees a 10% valuation fall, the LVR becomes about 88.9%, which may limit your options with some lenders.
Does interest only let me borrow more?
No. Lenders assess interest-only loans on principal and interest repayments over the remaining term after the interest-only period, so borrowing capacity is not increased.
Is the interest on my investment loan tax deductible?
Interest on money borrowed to buy or hold a rental property is generally deductible, but the principal part of repayments is not. Speak with your accountant about your situation.
