If you’re a landlord applying for a buy-to-let mortgage or remortgage in 2025, you’ll face two key hurdles: stress tests and affordability checks.

These lender assessments are designed to make sure your rental income is strong enough to cover mortgage repayments — even if rates rise. But for many landlords, they can be a source of confusion and frustration.

At NetRent, we help landlords every day understand lender requirements and secure the best mortgage deals. This guide explains exactly how stress tests and affordability checks work in 2025, and how to position yourself for success.

What Are Stress Tests?

A stress test is a calculation lenders use to ensure your rental income can cover your mortgage payments, not just at today’s rate, but if interest rates were to increase.

In 2025, lenders typically assume a notional interest rate of 5.5% to 6.5% when running affordability checks, even if the product you’re applying for is lower.

Example:

• Loan amount: £200,000

• Stress rate: 6%

• Monthly interest: £1,000

• Required rental income at 145% coverage: £1,450

If your property doesn’t generate at least that level of rental income, you may not pass the test.

What Are Affordability Checks?

Alongside stress testing, lenders assess your overall financial position. This may include:

• Your personal income (if applying in your own name)

• Other mortgages across your portfolio (for portfolio landlords)

• Property type and location (HMOs and flats can face stricter criteria)

• Tax status — whether you’re applying as an individual or through a limited company

Affordability checks ensure lenders aren’t taking on excessive risk, and that you’re not overstretching yourself financially.

2025 Requirements at a Glance

• Rental Coverage Ratios (ICRs): Typically 125% for basic-rate taxpayers, 145% for higher-rate taxpayers, and sometimes higher for HMOs or limited companies.

• Stress Rates: 5.5% to 6.5% depending on lender and product type.

• Portfolio Landlords: Lenders often review the entire portfolio’s performance, not just the property being mortgaged.

• Top Slicing: Some lenders may allow personal income to “top up” rental shortfalls — useful for landlords with strong earnings.

Why Stress Tests Are Tougher in 2025

With interest rates higher than in the 2010s, lenders are taking a cautious stance. This means:

• More landlords are finding their borrowing capacity reduced.

• Lower-yielding properties (such as in London and the South East) are more likely to struggle under stress test conditions.

• Specialist lenders are playing a bigger role, offering more flexible criteria where high-street banks say no.

How to Improve Your Chances of Passing

1. Increase rental income: Review whether your current rents are in line with the market.

2. Consider longer-term fixes: Some lenders use lower stress rates for 5-year fixed mortgages compared to 2-year deals.

3. Apply through a limited company: This can sometimes reduce the stress test threshold, making it easier to qualify.

4. Work with a specialist broker: A broker can identify lenders with more flexible criteria and structure your application for success.

Key Takeaways for Landlords

• Stress tests and affordability checks are central to every buy-to-let mortgage in 2025.

• Lenders want reassurance that you can weather higher interest rates.

• Affordability is judged on both property income and your wider financial situation.

• Specialist advice can make the difference between rejection and approval.

Need Help Passing the Stress Test?

Don’t let affordability hurdles hold you back from growing your portfolio. At NetRent, we specialise in helping UK landlords secure competitive buy-to-let and remortgage deals — even in today’s tougher lending environment.

Call us today on 01352 721300