When to Lock in a Fixed Rate Home Loan

A fixed rate loan makes the most sense when you can't afford the risk of rate rises during a specific window of time.

That window changes depending on where you are in life. A first home buyer stretching to get into Castle Hill might need certainty for the first three years while their income catches up. Someone mid-career with two kids and a decent offset balance might split the loan and lock half. A borrower nearing retirement might fix the whole thing to match their final working years. The question isn't whether fixed rates are good or bad. It's whether locking your rate solves a problem you actually have right now.

First Home Buyers: Fixing While Your Income Grows

When you're buying your first home, your borrowing capacity is usually calculated on what you earn today, not what you'll earn in two years. That gap between current income and future income is where fixed rates earn their keep.

Consider a buyer who purchased a townhouse in Castle Hill with a 10% deposit. Their household income at settlement was $120,000. Repayments at the variable rate were manageable, but only just. If rates rose by 1% in the first year, their monthly repayment would jump by around $400. They fixed for three years because they knew their income would grow through that period as one partner moved into a senior role, but they couldn't bank on it happening fast enough to absorb a rate rise in year one. By year three, their income had lifted to $145,000 and the fixed period ended. The rate had moved, but so had their capacity to handle it. Fixing gave them a predictable cost base during the years when they had the least financial flexibility.

If you're in a similar position, a three-year fixed term often aligns with the timeframe in which your income is most likely to increase, whether through progression, a second income returning after parental leave, or a career shift. First home buyers often underestimate how much their financial position will change in the first few years of ownership, and a fixed rate can smooth out that transition.

Mid-Career Borrowers: The Split Rate Approach

Once you've built some equity and your income is more stable, fixing the entire loan often makes less sense. You're not as vulnerable to rate movement, and you've usually got an offset account working to reduce interest on the variable portion.

A split loan lets you lock part of your debt while keeping the rest variable. The fixed portion gives you a floor on what your minimum repayment will be. The variable portion keeps your offset active and lets you make extra repayments without penalty. In our experience, borrowers in their mid-30s to mid-40s with established equity often split 50-50 or 60-40 in favour of variable, depending on how much they're putting into offset and how much rate movement they're prepared to wear. If you're regularly putting a few thousand into offset each month and your loan balance is dropping, you don't need the whole loan fixed. You need enough fixed to sleep at night and enough variable to let the offset do its work.

The other advantage of a split is that when your fixed term ends, only half your loan reverts at once. You're not stuck refinancing or negotiating the entire balance in a single hit. You've got options, and you're not forced into a decision because the whole loan just rolled to a higher revert rate.

Pre-Retirees and Retirees: Locking the Loan to Match Your Timeline

If you're within five years of retirement and still carrying a mortgage, your priority is usually certainty. Variable rates don't care that your income is about to drop or disappear.

A fixed rate lets you lock your repayment to match your remaining working years or your drawdown plan if you're already retired. Consider a borrower who retired at 63 with $280,000 still owing on their owner occupied home loan. They had super, but no wage income. They fixed for five years because that was the period over which they planned to draw down their super to clear the debt. The repayment was $1,850 a month, and it didn't move. They knew exactly how much to draw each year, and there was no risk of a rate rise forcing them to pull more out of super than they'd planned. At the end of the fixed term, the loan was paid off. The certainty cost them a bit more in interest compared to variable, but it removed the single biggest risk to their retirement plan, which was a rate spike in the first few years when they had the least flexibility.

Refinancing into a fixed rate in your final working years isn't about getting the lowest rate. It's about eliminating uncertainty during a stage of life when your income can't adjust to cover surprises.

How Long Should You Fix For

The right fixed term depends on how long you need the certainty, not what term the bank is promoting. One-year fixed rates are usually the lowest, but they only make sense if your situation is going to change within 12 months, such as an expected bonus, inheritance, or sale of another property. Three-year terms suit buyers who need breathing room while income grows or expenses drop, such as childcare ending. Five-year terms suit people who want to set and forget, particularly pre-retirees or anyone with a major financial commitment that won't shift for half a decade.

The longer you fix, the less flexibility you have. Break costs apply if you need to sell, refinance, or pay down the loan early. Most lenders calculate break costs based on the difference between your fixed rate and the current wholesale rate for the remaining term. If rates have dropped since you fixed, the break cost can run into the thousands. If rates have risen, the break cost is usually zero. You're not locked in forever, but you are locked in financially, and that trade-off matters more the longer the term.

Castle Hill has a large proportion of families and professionals who move for work or upsize within a few years. If there's any chance you'll sell or refin­ance before the fixed term ends, keep the term short or split the loan so only part of it is locked.

What Happens When Your Fixed Rate Ends

When the fixed period expires, your loan automatically moves to the lender's standard variable rate unless you do something about it. That revert rate is almost always higher than the variable rate the lender is offering to new customers, sometimes by 0.5% or more.

You've got a few options. You can refinance to a new lender and pick up a lower rate, particularly if your equity has improved. You can negotiate with your current lender and ask them to match a competitor's rate. Or you can fix again if your circumstances still suit it. The one thing you shouldn't do is let it roll to the revert rate and leave it there. We regularly see borrowers who fixed three years ago, forgot about it, and have been sitting on a revert rate that's costing them $200 to $300 a month more than they need to pay.

Set a reminder for 90 days before your fixed term ends. That gives you enough time to compare rates, get pre-approval elsewhere if needed, and negotiate without the pressure of a deadline. If you're planning to fix again, start the conversation early. Lenders usually let you lock in a new fixed rate up to 90 days before the current one expires, so you're not stuck waiting until the last minute and taking whatever rate is available on the day.

Fixed Rates and Offset Accounts Don't Mix

Most lenders don't offer offset accounts on fixed rate loans. If they do, the fixed rate is usually higher to compensate. That's not an oversight. It's a pricing decision. The lender is locking their cost of funds when they offer you a fixed rate, and they can't do that if you're reducing the interest-earning balance every month with an offset.

If you've built up savings or you're putting surplus income aside each month, a full fixed loan will cost you more than a variable or split loan with offset. The interest you save by keeping money in offset almost always outweighs the rate difference between fixed and variable unless you're fixing at an unusually low point in the cycle. For most people in Castle Hill with a mortgage and an offset balance above $30,000, a split loan is the better structure. Fix the portion you need for certainty, leave the rest variable, and keep your offset working on the variable portion.

When Not to Fix

Fixing makes sense when you need certainty. It doesn't make sense when you're chasing a rate that looks slightly lower than variable this month. If your income is solid, your expenses are predictable, and you've got a buffer in offset or savings, you probably don't need a fixed rate. The variable rate gives you full flexibility to make extra repayments, redraw if needed, and refinance or sell without break costs.

Fixed rates also don't suit borrowers who are likely to receive lump sums in the near term, such as inheritances, redundancy payouts, or the sale of an investment property. If you're planning to put $100,000 into the loan in 18 months, locking that loan for three years will trigger a break cost when you try to pay it down. You'll end up paying to get out of the certainty you paid to get into.

The other time to avoid fixing is when your loan structure isn't right yet. If you're still deciding whether to set up an offset, or you're planning to split your lending between owner-occupied and investment, or you're going to pull equity for renovations in the next year, lock that structure in first. Once you fix, changing anything becomes expensive.

Call one of our team or book an appointment at a time that works for you. We'll walk through your income, your timeline, and what you're actually trying to achieve, and we'll show you what a fixed rate, a split, or a variable loan would cost you in real terms. No fluff, just numbers and options that actually suit where you're at right now.

Frequently Asked Questions