Interest-only vs repayment mortgages: how they work and the risks

When you’re buying a home, the type of mortgage you choose affects not just your monthly payments, but also how and when the mortgage balance is cleared. Two common options are interest-only mortgages and repayment mortgages. Understanding the differences can help you judge which structure fits your long-term plans.

Important: A mortgage is a long-term commitment. Missing payments can lead to serious consequences, including repossession.

What is an interest-only mortgage?

An interest-only mortgage is designed so that, during the mortgage term, you pay only the interest charged on the loan. That means the loan balance does not reduce over time.

How payments work

• Each month you pay the interest portion.
• You do not pay down the amount you borrowed.
• At the end of the agreed term, you’re expected to repay the original loan amount (the capital) in full.

How the capital is repaid at the end

Lenders may accept different repayment methods, but the key point is that you must have a credible plan for clearing the outstanding balance when the term ends. Common approaches include:

• using savings
• selling the property
• using an investment or other arrangement (where applicable)

What is a repayment mortgage?

A repayment mortgage is structured so that each monthly payment includes:

• the interest, and
• a portion that reduces the capital (the amount borrowed)

How payments work

• Your monthly payment is typically higher than an interest-only mortgage.
• Over time, the mortgage balance reduces.
• By the end of the term, the mortgage is intended to be paid off in full.

The key difference: what happens to the loan balance?

The simplest way to compare the two is to look at the mortgage balance over time:

• Interest-only: balance stays broadly the same during the term; capital repayment is due at the end.
• Repayment: balance reduces gradually; capital is cleared through monthly payments.

This difference drives both the cashflow (monthly affordability) and the risk profile (what could go wrong later).

Risks to understand with interest-only mortgages

Interest-only mortgages can appeal if you want lower monthly payments, but they come with specific risks—particularly around the end of the term.

1) You may not have the capital when it’s due

Because you’re not paying down the loan during the term, the biggest concern is whether you can repay the outstanding balance at the end.

Potential issues include:

• investment values not performing as expected
• savings not building as planned
• changes to personal circumstances that reduce your ability to save

2) Selling the property may not solve the problem

Some borrowers intend to repay the capital by selling. However, sale prices can be affected by market conditions, and selling costs and delays can reduce the net amount available.

If property values fall or the sale takes longer than expected, the amount you receive may be insufficient to clear the mortgage.

3) Interest rates can still affect affordability

Even though you’re only paying interest, your monthly payment can be influenced by the mortgage’s interest rate structure (for example, if the mortgage is on a variable or tracker basis).

If rates rise, monthly payments can increase—potentially making the mortgage harder to sustain.

4) End-of-term planning can be overlooked

Interest-only mortgages require clear thinking about:

• the repayment method
• whether it remains realistic over time
• what happens if circumstances change

Without a robust plan, the end of the term can create a sudden, high-pressure financial event.

Risks to understand with repayment mortgages

Repayment mortgages are often viewed as “simpler” because the balance reduces over time. However, they still have risks.

1) Higher monthly payments

Because repayment mortgages include capital repayment, monthly payments are typically higher than interest-only. If your income changes, this can affect affordability.

2) Paying off the mortgage may take longer than expected

If you make only the minimum payments and your mortgage term is extended or you switch products later, the overall cost and timeline can change.

3) Early repayment charges may apply

Some mortgages include terms that affect what happens if you repay early or switch. This can be relevant when planning for future moves.

Which is “better” depends on your circumstances

There isn’t a single mortgage type that suits everyone. The right choice depends on factors such as:

• your budget and monthly affordability
• your long-term plan for the property
• how confident you are in repaying the capital at the end of an interest-only term
• your attitude to risk and uncertainty
• whether you have (or can build) a reliable repayment strategy

A mortgage adviser can help you compare options in the context of your goals and overall financial position.

Questions to consider before choosing

If you’re weighing up interest-only versus repayment, it can help to think through practical points such as:

• What will clear the capital at the end of the term (interest-only)?
• How certain is that plan, and what could disrupt it?
• How would your monthly payments cope if interest rates increased?
• Are you likely to move, and how would that affect repayment?
• What happens if your income changes or you need to reduce spending?

A note on suitability and planning

Interest-only mortgages can be appropriate for some borrowers, but they require stronger end-of-term planning than repayment mortgages. If you’re considering interest-only, it’s particularly important to understand the capital repayment risk and ensure your strategy is realistic.

Mortgage warning

YOUR HOME MAY BE REPOSSESSED IF YOU DO NOT KEEP UP REPAYMENTS ON A MORTGAGE OR ANY OTHER DEBT SECURED ON IT.