Can I still get an interest-only mortgage in the UK?

Yes, but with restrictions. Most lenders require 25–50%+ deposit, proof of a credible repayment vehicle, minimum loan size, and often a minimum income of £50,000–£75,000.

What happens if my repayment vehicle doesn't cover the capital?

Options include: switch to repayment mortgage, increase investment contributions, extend the term, or sell and downsize. The FCA actively encourages interest-only borrowers to review their repayment strategies.

Can I switch from interest-only to repayment mid-term?

Yes. Most lenders allow switching without early repayment charges. You can also split — part repayment, part interest-only. Your payments increase but the capital risk is eliminated.

Is an interest-only mortgage ever a good idea?

It can be for BTL investors (maximises cash flow), high earners with strong investment discipline, or property developers. For most residential borrowers without a solid repayment plan it carries significant risk.

UK Interest Only Mortgage Calculator

Calculate your monthly interest-only payment and project whether your repayment vehicle (ISA, pension, or endowment) will cover the capital outstanding at the end of the mortgage term.

Loan Amount

Interest Rate

Mortgage Term

yrs

Repayment Vehicle

Monthly Interest Payment

£938

Capital of £250,000 remains outstanding — projected shortfall at term end

Total Interest (25 yrs)

£281,250

Repayment Mortgage

£1,390/mo

Monthly Saving vs Repayment

£452

Capital to Repay

£250,000

How to Use This Interest Only Calculator

Enter your Loan Amount, Interest Rate, and Mortgage Term. Select your repayment vehicle type and click "More options" to enter the current value, expected growth rate, and monthly contributions to project whether your vehicle will cover the capital at term end.

What Is an Interest-Only Mortgage?

An interest-only mortgage means your monthly payments cover only the interest on the loan — none of the capital. At the end of the term, you still owe the full original loan amount and must repay it in one lump sum. This is why a credible repayment vehicle (a strategy to accumulate the capital) is essential.

FCA Rules on Repayment Vehicles

Since 2012, UK mortgage lenders must verify that borrowers have a credible repayment strategy before granting an interest-only mortgage. Acceptable vehicles include ISAs, pension lump sums, endowment policies, and proceeds from a property sale (including the mortgaged property itself, known as "sale of property").

Gap Analysis

The gap is the difference between your projected vehicle value at term end and the outstanding capital you owe. If there is a gap, you need to either increase contributions, choose a higher-growth vehicle, or consider switching to a repayment mortgage before the term ends.

Interest Only Mortgage Formulas

Monthly IO Payment = Loan Amount × (Annual Rate / 12)

Total Interest = Monthly IO Payment × (Term in Years × 12)

Repayment Vehicle Projection:
FV = PV × (1+r)^n + PMT × ((1+r)^n − 1) / r
Where: PV = current value, r = monthly growth rate,
n = months, PMT = monthly contribution

Gap = Loan Amount − Projected Vehicle Value

Example: Interest Only in London

Helen's London Interest-Only Mortgage

Helen has a £400,000 interest-only mortgage at 4.5% with 20 years remaining. She has a Stocks and Shares ISA currently worth £85,000 and contributes £500/month. Expected growth: 6% p.a.

Loan Amount	£400,000
Interest Rate	4.5%
Monthly IO Payment	£1,500
Total Interest (20 yrs)	£360,000
Repayment Mortgage (comparison)	£2,531/mo
Monthly Saving vs Repayment	£1,031
ISA Current Value	£85,000
ISA Monthly Contribution	£500
Projected ISA Value (6%, 20yr)	£503,000
Capital to Repay	£400,000
Surplus	£103,000

Helen's ISA is projected to cover her mortgage capital with a £103,000 surplus (at 6% growth). However, investment returns are not guaranteed — if growth averages only 4%, the projected value drops to £358,000, leaving a £42,000 shortfall. She should review this annually.

Frequently Asked Questions

Yes, but they are much harder to obtain than before 2012. Most mainstream lenders require: a minimum 25–50% deposit (low LTV), proof of a credible repayment vehicle with a documented strategy, a minimum loan size (often £150,000+), and often a minimum income of £50,000–£75,000. Some private banks and specialist lenders are more flexible, especially for high-net-worth borrowers.

If your vehicle falls short, you have several options: switch to a repayment mortgage now to start reducing capital; increase contributions to your investment vehicle; remortgage and release less money; extend the mortgage term; or sell the property at term end and downsize if the proceeds cover the outstanding capital. The FCA has been actively contacting interest-only mortgage holders (the "mortgage time bomb" cohort) to encourage action before their term ends.

Yes. Most lenders allow you to switch from interest-only to repayment without exiting your current deal or paying early repayment charges. You simply contact your lender and request the change. Your monthly payments will increase (as you start paying down capital), but you'll no longer have the risk of capital remaining at term end. You can also split — have part of the mortgage on repayment and part on interest-only.

It can be, in specific situations. For buy-to-let investors: IO maximises monthly cash flow and the interest is tax-deductible (partially). For high earners with strong investment discipline: the monthly saving can be invested to generate higher returns than the mortgage rate. For property developers or those planning to sell within the term: IO keeps costs low while the strategy is executed. For most residential homeowners without a solid repayment plan, it carries significant capital repayment risk.