The end of a fixed-rate mortgage deal is one of the most financially significant moments in homeownership, and one of the most frequently underestimated. People who leave it too late often pay thousands more than they need to. This guide walks you through exactly what to do and when, and lets you run the numbers with the free Loan Calculator by Zinsora.

What happens when your fixed rate ends?

When your fixed-rate period ends, your mortgage doesn't disappear, you still have an outstanding balance that needs to be refinanced. Your current lender will typically send you a rate lock offer. It feels easy to just accept it, but it's often not the best deal available.

At this point you also have an unusually free hand: you can switch lender without early repayment charges, reset your repayment rate and make an unlimited lump-sum overpayment, something you may not have been able to do freely during the fixed-rate period.

Key timing: Start shopping around at least 6 months before your deal ends. Many lenders let you lock in a new rate up to 6 months early, useful if rates are rising.

Your three options

Option 1: Rate lock with your existing lender

Your lender offers you a new rate, you accept and carry on. This is the path of least resistance, but not necessarily the cheapest. Lenders know that most borrowers stay out of inertia, and they price their retention offers accordingly. Always negotiate and get at least two quotes from other lenders before signing anything.

Option 2: Refinance to a new lender

You switch your mortgage to a different lender, often an online or direct lender with lower overheads. There are some upfront costs (legal fees, valuation) of around $500–1,500, but the savings from a better rate can easily outweigh these over a few years.

Example: Rate lock vs. refinance

Outstanding balance: $180,000 · Remaining term: 15 years

Lender A (rate lock): 4.5% → Monthly payment: $1,377 · Total interest: $67,860

Lender B (refinance): 4.1% → Monthly payment: $1,330 · Total interest: $59,400

Saving: $8,460 over 15 years, minus roughly $500 in switching costs = $7,960 net.

Option 3: Overpayment combined with remortgaging

The most powerful option: when your fixed rate ends, there is typically no limit on how much you can overpay. During the fixed-rate period you may have been capped at 10% per year. At expiry that restriction lifts. If you have savings available, putting a lump sum into the mortgage at this point reduces the balance you need to refinance, cutting both your monthly payment and total interest.

Overpaying before the deal ends

The transition point between fixed-rate deals is often the single best moment to make a large overpayment, no penalty, no limit.

What does a $20,000 overpayment save?

Outstanding balance: $180,000 → after overpayment: $160,000 · New rate: 4.2% · Term: 20 years

Without overpayment: $1,105/month · Total interest: $85,200

With $20,000 overpayment: $982/month · Total interest: $75,680

Saving: $123/month and $9,520 in total interest over 20 years

Whether overpaying beats investing depends on your mortgage rate. If your new rate is above 4–5%, overpaying almost always wins on a risk-adjusted basis. For a detailed comparison, see the guide on Mortgage Overpayment vs. Investing.

Is switching lender worth it?

Usually yes, if the rate difference is at least 0.2–0.3%. The typical costs of switching are:

Tip: Get quotes from comparison sites like Bankrate, LendingTree or Credible, then take the best rate back to your current lender. They'll often match it to keep your business.

Online and direct lenders tend to offer the keenest rates because they have lower operating costs. Credit unions are worth checking too, they often have competitive products for existing borrowers.

Checklist: 12 months before expiry

If you miss the expiry date entirely, your mortgage automatically rolls onto the lender's Adjustable Rate (ARM), usually 1–2% higher than fixed rates and changeable at any time. Set a reminder now.