BTL Remortgage UK 2026 — Complete Landlord Guide to Buy-to-Let Remortgaging, ICR, and Portfolio Rules

The Interest Coverage Ratio (ICR) stress test — how lenders assess BTL remortgage applications

The ICR is the primary affordability mechanism lenders use to assess BTL mortgage applications. Unlike residential mortgages (which use income multiples and personal affordability), BTL mortgages are primarily assessed on the rental income generated by the property:

• What the ICR is: The ICR is the ratio of the property's gross monthly rental income to the monthly mortgage payment at the lender's stress rate. For example, if a property generates £1,000 per month rent, and the lender stress tests at 5.5%, the maximum loan on a 25-year interest-only basis at a monthly payment of £1,000 would be £1,000 ÷ 5.5% × 12 ÷ 125% = approximately £174,500. Lenders typically require the ICR to be at least 125% (for basic rate taxpayers) or 145% (for higher rate taxpayers — reflecting Section 24 mortgage interest restrictions that reduce net rental income for higher-rate taxpayers)
• The stress rate: Lenders apply a stressed interest rate that is typically 1-2% above the current prevailing fixed rate, with a floor of approximately 5.5%. This stress rate is designed to test affordability under a rising rate scenario. In the current (mid-2026) market, most lenders use a stressed rate of 5.5-6% regardless of the actual product rate offered. This means that a landlord remortgaging to a product at 4.5% still has their ICR assessed at 5.5-6%
• ICR for higher-rate taxpayers and Section 24: Since the phasing in of Section 24 mortgage interest relief restrictions from 2017 (fully in effect from 2020 onwards), individual landlords who pay higher-rate income tax can no longer deduct mortgage interest from rental income — they receive only a 20% basic rate tax credit. This reduces their net rental income after tax. Many lenders reflect this by applying a higher ICR threshold (145%) for higher-rate taxpayer applicants, making it harder to borrow the same amount as a lower-rate taxpayer
• Rental income verification: Lenders require evidence of rental income — typically a current tenancy agreement showing the rental amount, the most recent 12 months of bank statements showing rental income credits, or an ARLA-qualified letting agent's rental valuation letter. Projected rental income for an unlet property is assessed by some lenders at up to 75-80% of the agent's projected rental valuation
• Calculating whether a remortgage is feasible: Before approaching a lender, calculate: (current monthly rent × 12) ÷ (stress rate %) ÷ ICR threshold = maximum loan. If this figure is below your outstanding loan balance, you will need to make a capital repayment at remortgage or accept a higher LTV product (if available)

Portfolio landlord remortgage — PRA 2017 additional underwriting requirements

Landlords with 4 or more mortgaged buy-to-let properties are classified as 'portfolio landlords' under the PRA 2017 rules. Portfolio landlords face more onerous underwriting when remortgaging:

• What counts toward the 4-property threshold: The threshold is 4 or more mortgaged buy-to-let properties. Unencumbered (mortgage-free) properties owned by the landlord do not count toward the portfolio threshold. Properties held in a limited company (SPV) do count if the landlord provides personal guarantees. Properties jointly owned with a non-portfolio spouse may or may not count depending on the lender's policy
• Portfolio Business Plan requirement: Most lenders require portfolio landlords to provide a Portfolio Business Plan — typically a schedule of all properties in the portfolio showing: property address; current market value; outstanding mortgage balance; monthly rental income; monthly mortgage payment; gross yield; and ICR per property. This allows the lender to assess the overall health of the portfolio, not just the specific property being remortgaged
• Rental coverage across the portfolio: Lenders assess not only the ICR of the property being remortgaged but also the aggregate ICR across the entire portfolio. Where some properties in the portfolio are cashflow-negative (rental income is below the stressed mortgage payment), the lender may require the landlord to demonstrate that the portfolio as a whole remains ICR-compliant
• Asset and liability schedule: Portfolio landlords are typically required to provide a full personal asset and liability statement — including all properties, associated mortgages, and other liabilities. This is assessed alongside the portfolio income to determine whether the remortgage is sustainable
• Specialist portfolio lenders: Not all mainstream BTL mortgage lenders will lend to portfolio landlords — many limit their portfolio landlord exposure. Specialist portfolio lenders include Paragon, Fleet Mortgages, Foundation Home Loans, Shawbrook, and Interbay. These lenders typically offer higher LTV products (up to 80%), accept properties in limited company structures, and have dedicated portfolio underwriting teams

Product transfer vs full remortgage — when each approach is appropriate

At the end of a fixed-rate BTL product, landlords have two options: a product transfer with the existing lender, or a full remortgage to a new lender. The choice depends on rates, underwriting requirements, costs, and property circumstances:

• Product transfer (rate switch with existing lender): A product transfer is where the landlord switches to a new rate with the existing lender without any new underwriting. The lender does not re-assess the ICR, the property value, or the landlord's personal circumstances — the loan simply moves to a new interest rate from the existing balance. Product transfers are typically faster (days vs weeks), cheaper (no valuation, legal fees, or arrangement fees in many cases), and available even where the property's rental income would not pass the current ICR test on a full remortgage (because there is no re-underwriting). They are the preferred option for landlords who may face ICR challenges on a full remortgage
• Full remortgage to a new lender: A full remortgage involves a new lender conducting full underwriting — new valuation, ICR assessment, income verification, credit checks. Full remortgages allow the landlord to: increase the loan (release equity); switch from interest-only to capital repayment; change the LTV; or access a product not available on product transfer. Full remortgages are appropriate where the landlord wants to release equity for a further purchase, where the existing lender's rates are uncompetitive, or where the landlord wants to consolidate into an SPV limited company structure
• Early Repayment Charges (ERCs): Fixed-rate BTL mortgages typically carry an ERC (often 2-5% of the outstanding loan balance) payable if the mortgage is repaid or switched during the fixed-rate period. ERCs make it expensive to exit a product early. For a £200,000 loan with a 3% ERC, the cost of early exit is £6,000. Landlords should compare the ERC cost against the interest saving from switching to a lower rate product — sometimes it is cost-effective to pay the ERC if the rate saving is significant
• Timing the remortgage — when to start the process: Full BTL remortgages typically take 6-12 weeks from application to completion (longer for portfolio landlords). Landlords should begin exploring remortgage options 3-6 months before their fixed-rate product ends. Many lenders allow a remortgage offer to be locked in 3-6 months in advance, protecting against rate rises before completion

Limited company (SPV) BTL remortgages — special considerations

Many landlords have restructured their portfolios into special purpose vehicle (SPV) limited companies to mitigate the impact of Section 24 mortgage interest restrictions. SPV companies have different BTL mortgage options and underwriting requirements:

• SPV lending market: Not all BTL lenders lend to SPV limited companies — the SPV lending market is more limited than the individual BTL market. Major SPV BTL lenders include Paragon, Foundation Home Loans, Fleet Mortgages, Shawbrook, and The Mortgage Works. SPV rates are typically 0.1-0.5% higher than equivalent individual BTL rates, reflecting the additional complexity and perceived risk
• ICR assessment for SPV companies: Lenders assess SPV BTL applications on the property rental income vs the mortgage payment, as with individual BTL applications. However, many lenders apply a lower ICR threshold (125% regardless of corporation tax rate) for SPV companies — reflecting that SPV companies pay corporation tax (lower rate than higher-rate income tax) and are not subject to Section 24 restrictions
• Personal guarantees: SPV BTL lenders almost universally require personal guarantees from the directors/shareholders of the SPV. The personal guarantee means that the director is personally liable for the SPV's mortgage obligations if the SPV defaults. This significantly reduces the liability protection that limited company status would otherwise provide in a worst-case scenario
• Transferring existing individual BTL properties into SPV — SDLT and CGT: Transferring an existing BTL property from personal name into an SPV company is treated as a disposal for CGT purposes (at the market value) and a purchase for SDLT purposes (including the SDLT 5% surcharge on residential property from October 2024). The SDLT and CGT costs of incorporation can make direct transfer unattractive — specialist advice from a tax adviser is essential before implementing any portfolio incorporation strategy

Frequently asked questions