How BTL Affordability Works
Buy to Let mortgage affordability is assessed very differently from residential mortgages. Instead of
focusing primarily on your personal income, lenders assess whether the rental
income can cover the mortgage payments with sufficient margin.
Key factors lenders consider:
- Rental Income: The expected monthly rent from the property
- Interest Coverage Ratio (ICR): The ratio of rental income to mortgage payment
- Stress Testing: Lenders test affordability at higher interest rates than the
actual rate
- Loan to Value (LTV): The percentage of the property value you're borrowing
- Your Tax Status: Basic rate vs higher rate taxpayers have different
requirements
- Property Portfolio: Owning multiple BTL properties affects assessment
Most lenders require rental income to be 125-160% of the mortgage payment (calculated at a stressed
interest rate), depending on your circumstances.
What is ICR and Why Does It Matter?
Interest Coverage Ratio (ICR) is the cornerstone of BTL lending. It measures whether
your rental income provides adequate coverage for the mortgage payments.
How ICR is calculated:
ICR = (Annual Rental Income ÷ Annual Mortgage Payment) × 100
Required ICR levels vary by borrower type:
- Basic Rate Taxpayers (Personal Name): Typically 125% ICR required
- Higher Rate Taxpayers (Personal Name): Typically 145% ICR required
- Portfolio Landlords (4+ properties): 160% or higher ICR required
- Limited Company Ownership: Usually 125% ICR, regardless of personal tax status
Example: If your annual rental income is £15,000 and your annual mortgage payment
(at the stress test rate) is £10,000, your ICR is 150%. This would pass for basic rate taxpayers
(125% required) and higher rate taxpayers (145% required).
Why it matters: ICR protects both you and the lender. It ensures there's a buffer
for void periods, maintenance costs, and interest rate increases. A higher ICR means more financial
security for your investment.
Understanding Stress Testing
Lenders don't assess affordability at your actual mortgage rate. They use stress
testing - calculating whether you can afford payments at a higher interest rate.
Why stress testing exists:
- Protects you from future interest rate rises
- Ensures the investment remains viable in different economic conditions
- Required by financial regulations to promote responsible lending
How it works in this calculator:
- 5-Year Fixed Rates: Tested at the actual rate you enter
- 2-Year Fixed Rates: Tested at the rate you enter PLUS 2%
Example: If you're getting a 2-year fixed rate at 5.5%, the calculator tests whether
your rental income can cover payments at 7.5%. This higher rate is used only for the affordability
test - your actual payments will be at 5.5%.
Loan to Value (LTV) Explained
Loan to Value (LTV) is the percentage of the property value that you're borrowing.
The remainder is your deposit.
How LTV works:
- 75% LTV = 25% deposit required
- 80% LTV = 20% deposit required
- 85% LTV = 15% deposit required
Impact on interest rates:
- Up to 75% LTV: Best rates available
- 75-85% LTV: Rates typically increase by 0.3-0.8%
- Above 85% LTV: Very limited lenders, significantly higher rates (if available
at all)
Strategic consideration: While higher LTV means lower deposit, the higher interest
rate can significantly impact your returns. Many investors find 75% LTV offers the best balance of
leverage and affordability.
