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How do I calculate the monthly repayments for a RIO mortgage?

13th February 2026

By Simon Carr

Retirement Interest-Only (RIO) mortgages are designed for older homeowners who want to release or retain capital in their property but need to ensure they can afford ongoing payments. Unlike standard mortgages where you repay both interest and capital, RIO repayments cover only the monthly interest accrued on the borrowed capital. Calculating these payments involves a relatively straightforward application of the interest rate to the remaining loan balance, ensuring the borrower’s retirement income is sufficient to meet these monthly obligations for the duration of the loan.

How Do I Calculate the Monthly Repayments for a RIO Mortgage?

A Retirement Interest-Only (RIO) mortgage allows homeowners, typically over the age of 55, to borrow against their property without the requirement to pay back the principal capital until a predefined life event occurs. Because the payments are strictly interest-only, the calculation is significantly simpler than calculating the repayments for a standard capital repayment mortgage.

The fundamental principle is determining the cost of borrowing the money for one month.

Step-by-Step: Determining Your RIO Repayment Amount

The calculation requires three pieces of information: the loan amount, the annual interest rate, and the frequency of payments (which is typically monthly).

1. Confirm the Total Loan Balance and Annual Interest Rate

The loan balance is the total amount you have borrowed. The interest rate is usually expressed as an Annual Percentage Rate (APR). You must use the actual interest rate agreed upon with the lender, ensuring you account for any initial fixed-rate period or potential subsequent variable rates.

For example, assume you borrow £100,000 at an annual interest rate of 5%.

2. Calculate the Annual Interest Cost

First, convert the annual interest rate percentage into a decimal by dividing it by 100 (e.g., 5% becomes 0.05). Then, multiply the total loan balance by the decimal interest rate.

  • Loan Balance: £100,000
  • Annual Rate (Decimal): 0.05
  • Annual Interest Cost: £100,000 x 0.05 = £5,000

This £5,000 represents the total interest charged over one year.

3. Determine the Monthly Repayment

Since RIO mortgage payments are made monthly, divide the annual interest cost by 12 (the number of months in a year) to find your monthly repayment obligation.

  • Annual Interest Cost: £5,000
  • Monthly Repayment: £5,000 / 12 = £416.67

Therefore, if you take out a £100,000 RIO mortgage at 5%, your monthly repayment is £416.67. This payment covers the interest completely, meaning the principal loan balance remains exactly £100,000 throughout the life of the mortgage (assuming no voluntary overpayments are made).

The Impact of Rate Types on RIO Calculations

While the calculation method remains the same, the actual monthly figure may change depending on whether your RIO mortgage has a fixed or variable interest rate.

Fixed-Rate RIO Mortgages

If you secure a fixed rate (e.g., 5% fixed for five years), your monthly repayment figure will remain consistent for that fixed period, providing budgeting certainty. After the fixed term expires, the rate will typically switch to the lender’s Standard Variable Rate (SVR), and the monthly repayment will need to be recalculated based on the new, often higher, SVR.

Variable-Rate RIO Mortgages

If your mortgage is on a variable rate, your interest rate can fluctuate according to changes in the market, often influenced by the Bank of England Base Rate. This means your monthly repayment must be recalculated every time the variable rate changes. This introduces greater risk but can result in lower payments if interest rates fall.

Understanding Affordability and the RIO Application Process

A critical component of obtaining a RIO mortgage is passing the lender’s affordability checks. Unlike standard interest-only mortgages where lenders historically accepted a plan to repay the capital, RIO lenders are solely focused on whether the applicant can definitively afford the monthly interest payments until the capital is eventually repaid (often upon the second borrower’s death or entry into long-term care).

Lenders will typically stress-test your application to ensure you could still afford the payments even if the interest rate were to rise significantly in the future. They will scrutinise all sources of retirement income, including:

  • State Pension
  • Private or Occupational Pensions
  • Investment Income (e.g., rental income or dividend payments)
  • Certain long-term benefits

Creditworthiness and RIO Affordability

As with any secured borrowing, lenders will review your credit history to assess your reliability in managing debt. A healthy credit score improves your chances of acceptance and accessing the best rates. Understanding what lenders see is vital:

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Affordability requirements for RIO mortgages are often stringent, reflecting the long-term nature of the commitment and the need for consumers to be protected from financial difficulty during retirement. For official guidance on planning for retirement and managing later-life debt, consult reliable sources like the government-backed MoneyHelper service.

The Principal Repayment Strategy

A key feature of the RIO mortgage that differentiates it from standard mortgages is that the principal loan balance does not decrease through monthly payments; it is repaid only after a specified life event occurs. This typically happens when the last remaining borrower either dies or moves into permanent long-term residential care.

At this point, the property must be sold, and the proceeds are used to pay off the outstanding loan balance. It is crucial to understand that if property values fall, or if selling costs are high, the debt must still be repaid in full.

Risks and Compliance Considerations

While RIO mortgages offer an effective way for older homeowners to manage their finances, it is essential to be aware of the associated risks and responsibilities.

Interest Rate Risk

If you have a variable rate or come to the end of a fixed-rate period, your interest rate could increase substantially. As RIO affordability is based purely on your ability to cover the interest, a significant rate increase could push your monthly repayments beyond what your retirement income can comfortably sustain.

Consequences of Default

Failing to make the required monthly interest payments constitutes a default on the mortgage agreement. This can have serious consequences. Lenders may initiate legal action, increase interest rates, or apply additional charges. Crucially, if you consistently fail to meet your obligations:

Your property may be at risk if repayments are not made. This could ultimately lead to repossession, resulting in the loss of your home.

Impact on Inheritance

Since the entire principal balance is repaid only upon sale, the amount of equity remaining in the property (and therefore the potential inheritance left to beneficiaries) depends heavily on the property’s value at the time of sale compared to the outstanding debt.

People also asked

Is a RIO mortgage the same as equity release or a Lifetime Mortgage?

No, they are different. A traditional lifetime mortgage (a form of equity release) usually allows the interest to roll up and compound over time, meaning there are no monthly payments required. A RIO mortgage requires the borrower to make mandatory monthly interest payments throughout the life of the loan, ensuring the debt does not increase.

What criteria determine eligibility for a RIO mortgage?

Eligibility is primarily based on age (typically 55+) and, most importantly, affordability. Lenders need firm evidence that your sustainable retirement income (pensions, investments, etc.) is sufficient to cover the required monthly interest payments, even if rates rise.

Can I make voluntary capital repayments on a RIO mortgage?

Yes, many RIO mortgages allow for voluntary overpayments, often up to a specific percentage of the outstanding balance annually, without incurring early repayment charges (ERCs). Making overpayments helps reduce the total amount owed, lessening the burden on your beneficiaries when the property is eventually sold.

What happens if one joint borrower dies?

In a joint RIO mortgage, the loan continues seamlessly with the remaining borrower, provided they meet the lender’s affordability criteria on their own. The principal loan only becomes repayable upon the death or entry into care of the last surviving borrower named on the agreement.

Does the RIO mortgage balance ever change?

If you only pay the required monthly interest, the principal loan balance remains constant. The balance only changes if you make voluntary capital overpayments (reducing the debt) or if you miss payments, leading to fees and potentially rolled-up interest charges being added to the outstanding balance.

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