The two decisions that define your mortgage
Every mortgage bundles two distinct decisions together. The first is your repayment method: repayment or interest-only. This decides whether each monthly payment chips away at the debt or just covers the interest, and it determines whether you own the home outright at the end of the term.
The second is your interest-rate type: fixed, tracker, discount, standard variable or offset. This decides how predictable your payments are from month to month and how exposed you are when the Bank of England moves its base rate. Getting both decisions right for your budget and risk appetite matters more than chasing the single lowest headline rate.
In practice, the vast majority of UK residential buyers choose a repayment mortgage on a fixed-rate deal of two or five years. The fixed rate delivers certainty while the deal lasts, and the repayment structure means you are steadily paying down what you owe. But for some buyers, a tracker, offset or interest-only arrangement works out significantly cheaper or more flexible, particularly for buy-to-let investors, people with large savings, or those who plan to move or remortgage soon.
Mortgage interest types compared
These are the main ways the interest rate can be structured on a UK mortgage.
| Type | How it works | Best for | Watch out for |
|---|---|---|---|
| Fixed rate (2-year) | Rate locked for 2 years | Short-term certainty; planning to move soon | Early repayment charges; higher remortgage frequency |
| Fixed rate (5-year) | Rate locked for 5 years | Long-term certainty; dislike payment changes | Higher ERCs if you need to leave early |
| Tracker | Follows base rate + a set margin | Expecting rate falls; flexibility wanted | Payments rise if base rate rises |
| Standard variable (SVR) | Lender sets and changes the rate freely | Short-term after a deal ends | Usually the most expensive option; unpredictable |
| Discount | Set discount off the lender's SVR | Lower early payments than fixed | SVR can move so payments vary |
| Offset | Savings balance reduces interest charged | Savers with a cash buffer | Slightly higher headline rate than equivalent fixed |
When a fixed, tracker or discount deal ends, you usually roll onto the lender's SVR, which is often 2 to 4 percentage points higher than new deals.
Repayment mortgages in detail
With a repayment (or capital and interest) mortgage, each monthly payment is split between interest and capital. In the early years of the mortgage, most of each payment goes towards interest and only a small portion reduces the balance. As the years pass and the debt falls, the proportion going to capital grows. By the final payment, you own the property outright.
This structure is the safest option for most residential buyers because there is no separate vehicle or savings plan needed at the end. Your equity grows with every payment you make, and lenders are comfortable lending on this basis because the risk reduces over time.
On a £250,000 repayment mortgage at 4.5% over 25 years, monthly payments would be around £1,390. Total interest paid over the life of the loan would be approximately £167,000. Shortening the term to 20 years raises payments to roughly £1,580 but cuts total interest to around £129,000.
Interest-only mortgages: who they suit
With an interest-only mortgage you pay only the interest each month, so the full capital balance remains at the end of the term and must be repaid in full. Monthly payments are lower: on the £250,000 example above at 4.5%, you would pay around £938 a month instead of £1,390. However, you still owe £250,000 at the end.
Residential lenders are now cautious about interest-only mortgages and typically require a credible, evidenced repayment plan, such as an investment portfolio, endowment, or plans to downsize. By contrast, buy-to-let mortgages are very commonly on an interest-only basis, with landlords expecting to repay the loan from the proceeds when the property is sold.
If you are considering interest-only, confirm your repayment strategy is realistic and that your lender accepts it. Part-and-part mortgages, which split the loan between repayment and interest-only, offer a middle ground if you want lower monthly payments but still want to reduce some of the balance.
Specialist mortgage types
Beyond the mainstream, some buyers need a product built for their specific situation:
- Guarantor or joint borrower sole proprietor: a family member supports affordability without going on the title.
- Shared ownership mortgages: designed for part-buy, part-rent purchases through a housing association.
- Self-build mortgages: funds released in stages as construction progresses, assessed differently from standard mortgages.
- Buy-to-let mortgages: assessed primarily on projected rental income rather than personal income; usually interest-only.
- Retirement interest-only (RIO): for older borrowers, with the loan repaid from sale proceeds or on death.
- Right to Buy and Help to Buy mortgages: tailored for specific government home-ownership schemes.
Watch the end of your fixed period
When a fixed, tracker or discount deal ends you usually roll onto the lender's SVR, which is often several percentage points higher than current market deals. Start shopping for a remortgage three to six months before your deal ends to avoid a payment spike. Most lenders let you lock in a new deal in advance without paying it until your current deal expires.