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    Limited Company Mortgage Calculator: Maximum SPV BTL Loan in 2026

    A limited company mortgage calculator is the starting point for any UK landlord buying through a Special Purpose Vehicle (SPV). Unlike residential mortgages — which lean on income multiples — SPV buy-to-let lending is driven by Interest Coverage Ratio (ICR) stress tests on the rental income. This guide explains the calculator inputs, the formulas UK lenders actually use, the ICR thresholds in 2026, worked examples across property values and yields, and the lender-specific tweaks that change the answer.

    First Rung Now Editorial Updated 15 June 2026 7 min read

    The maths a limited company mortgage calculator uses

    Every SPV BTL lender uses essentially the same ICR formula:

    Maximum loan = (Annual rent ÷ ICR percentage) ÷ Stressed interest rate

    Then check against the LTV cap. Take the lower of the two.

    Worked example 1: £150,000 flat at £900/month rent

    • Annual rent: £10,800
    • ICR at 125%: £10,800 ÷ 1.25 = £8,640 (maximum stressed annual interest)
    • Stressed rate 5.5%: £8,640 ÷ 0.055 = £157,090 max loan by ICR
    • 75% LTV cap: 75% × £150,000 = £112,500 max loan by LTV
    • Maximum loan: £112,500 (LTV bites first — typical for higher-yield property)
    • Deposit needed: £37,500 + SDLT and fees

    Worked example 2: £250,000 house at £1,250/month rent

    • Annual rent: £15,000
    • ICR at 125%: £15,000 ÷ 1.25 = £12,000
    • Stressed rate 5.5%: £12,000 ÷ 0.055 = £218,182 max loan by ICR
    • 75% LTV cap: £187,500
    • Maximum loan: £187,500 (LTV still bites)

    Worked example 3: £400,000 London flat at £1,500/month rent

    • Annual rent: £18,000
    • ICR at 125%: £18,000 ÷ 1.25 = £14,400
    • Stressed rate 5.5%: £14,400 ÷ 0.055 = £261,818 max loan by ICR
    • 75% LTV cap: £300,000
    • Maximum loan: £261,818 (ICR bites — typical for low-yield London property)
    • Effective LTV: 65% — buyer needs £138,182 deposit, not the £100,000 they planned

    Stressed rate variations by lender and product

    • 5-year fixed products: Most lenders stress at the product pay-rate (e.g. 5.6%) rather than 5.5%. This often unlocks larger loans for landlords prepared to fix for 5 years.
    • 2-year fixed and trackers: Stressed at 5.5% or product-rate + 2%, whichever is higher.
    • Top-slicing lenders (Landbay, Paragon, Foundation): Allow personal income to supplement ICR if rental falls short. Useful on low-yield property.

    ICR variations: where 125% becomes 140% or 160%

    • HMO and MUFB: typically 140%–160% ICR.
    • Expat/non-resident SPV directors: typically 140% ICR.
    • Holiday let SPV: typically 145% on lower of 30%-occupancy or AST market rent.

    What the calculator doesn't capture

    1. Director credit footprint. Adverse credit reduces lender choice even if ICR maths passes.
    2. SPV age and structure. Trading companies and multi-director SPVs have narrower lender pools.
    3. Property type and tenant covenant. Studios, ex-LA flats, high-rise and HMO often face additional overlays.
    4. Portfolio stress. If you already own 4+ BTL properties, the lender may apply a portfolio aggregate ICR.
    5. Director income minimums. Most lenders require £25k–£30k personal income — calculator output is moot if you fail this gate.

    Putting it into action

    1. Plug your rental income and property value into the formula above.
    2. Take the lower of (ICR-derived loan, LTV-derived loan).
    3. Subtract from property value to get minimum cash deposit.
    4. Add ~10%–12% for SDLT (incl. 5% surcharge), legal, valuation and arrangement fees.
    5. Confirm with a broker which 3–5 lenders fit your specific case.

    Pros

    • Simple, transparent formula based on rent and stressed rate.
    • Lets you sense-check viability before committing time to applications.
    • Helps you identify whether ICR or LTV is the binding constraint.
    • Same maths works across SPV BTL, HMO and MUFB with different ICR.
    • Quickly shows when top-slicing or 5-year fixes will help.

    Cons

    • Doesn't capture lender-specific overlays.
    • Ignores director credit, SPV age and structure issues.
    • Stressed rate assumption may differ from what the lender actually uses.
    • HMO/holiday-let cases need higher ICR not built into vanilla calculators.
    • Portfolio aggregate stress (4+ properties) needs lender-specific modelling.

    Frequently asked questions