Repayment or Interest-Only? What You Owe at the End
The difference is not subtle and it is regularly mis-sold as a matter of monthly affordability. A repayment mortgage clears the loan over the term. An interest-only mortgage does not reduce the balance at all — at the end of twenty-five years you owe exactly what you borrowed on day one.
That is not automatically a bad arrangement. It is a bad arrangement without a credible plan for the balance, which is what went wrong on a large scale in several markets.
The two structures side by side#
| Repayment | Interest-only | |
|---|---|---|
| Monthly payment | Higher | Lower |
| Balance after 10 years | Reduced substantially | Unchanged |
| Balance at end of term | Zero | The full original amount |
| Total interest paid | Lower | Higher — interest is charged on the full balance throughout |
| Who it suits | Almost everyone buying a home | Specific cases with a repayment vehicle |
| Main risk | Payment size | Having no way to repay the capital |
The total interest line is the one people miss. Because the balance never falls, interest is charged on the full amount every month for the whole term — an interest-only loan costs more in total despite costing less each month.
The arithmetic#
Borrow 200,000 at 4.8% over 25 years. On repayment, the monthly payment is about 1,146 and total interest is roughly 143,800; at the end you own the house outright. On interest-only, the payment is 800 — the interest alone — total interest is 240,000, and at the end you still owe the 200,000.
- Monthly saving on interest-only: about 346, or thirty per cent of the payment.
- Extra total interest: roughly 96,000 over the term.
- Outstanding at the end: 200,000, which must come from somewhere.
- The saving is real and the cost of it arrives all at once, twenty-five years later.
Who interest-only genuinely suits#
There are legitimate cases, and they share a feature: a credible, evidenced plan for repaying the capital that does not depend on hoping.
- Buy-to-let investors, where the rent covers interest and the property is expected to be sold or refinanced.
- Borrowers with a genuine repayment vehicle — an investment portfolio, a pension lump sum, a maturing policy — that the lender will assess.
- Borrowers expecting to downsize, with enough equity that the sale plainly covers the balance.
- Very high or lumpy incomes where the capital is repaid in irregular lump sums.
- Short-term bridging situations, where the loan is explicitly temporary.
Notice what is not on this list: making an expensive house affordable. That is the use case that produced the mis-selling scandals, and lenders in most regulated markets now require the repayment plan to be evidenced at application.
The part-and-part option#
Splitting the loan — part repayment, part interest-only — is available in several markets and is underused. It reduces the payment relative to full repayment while guaranteeing that a defined portion of the debt is cleared regardless of what happens to the plan for the rest.
| Structure on 200,000 | Monthly payment | Owed at end |
|---|---|---|
| Full repayment | About 1,146 | 0 |
| 75% repayment, 25% interest-only | About 1,059 | 50,000 |
| 50/50 | About 973 | 100,000 |
| Full interest-only | 800 | 200,000 |
Illustrative, 4.8% over 25 years. The middle rows are the honest compromise: real payment relief, bounded end-of-term exposure.
Questions to ask before choosing interest-only#
- What exactly repays the capital, and what happens if it underperforms?
- Will the lender accept that vehicle as evidence, and how often will it be reviewed?
- What is the total interest over the term, compared with repayment?
- Could you switch to repayment later, and what would the payment become?
- If the plan is to sell, what fall in property prices would break it?
- Would part-and-part achieve most of the payment relief with far less risk?
If question one has no specific answer, the product is not suitable, however attractive the monthly figure looks.
Frequently asked questions
What is the difference between repayment and interest-only?
A repayment mortgage clears the loan over the term: each payment covers the interest and reduces the balance, so at the end you owe nothing. An interest-only mortgage pays the interest alone, so the balance never falls — at the end of the term you still owe exactly what you borrowed and must repay it in one lump. The monthly payment is lower, but the total interest is much higher, because interest is charged on the full balance for the whole term.
Is an interest-only mortgage a bad idea?
Not inherently — it is a bad idea without a credible plan for repaying the capital. It works for buy-to-let investors expecting to sell or refinance, for borrowers with an evidenced repayment vehicle such as an investment portfolio or a pension lump sum, and for people who plan to downsize with substantial equity. It fails when it is used simply to make an expensive property affordable, which is what produced the mis-selling problems in several markets and why lenders now require the repayment plan to be evidenced.
Can I switch from interest-only to repayment?
Usually yes, and most lenders will accommodate it because it reduces their risk. The payment will rise substantially, and the rise is steeper the later you switch, because the same capital has to be cleared over fewer remaining years. Some lenders allow a partial switch — converting part of the balance to repayment — which is a practical middle step if the full payment would be uncomfortable.
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