Securing a mortgage in the £5 million to £20 million range has always required a level of preparation, financial strength, and presentation far beyond what most mainstream lenders expect. In 2025, this segment of the lending market has become even more nuanced as private banks refine their criteria and specialist lenders innovate to attract sophisticated borrowers.
These large loans are typically associated with Prime Central London property, luxury country homes, major relocations, or strategic refinancing. But with higher interest rates, changed affordability rules, and increased regulatory oversight, the path to securing a substantial mortgage has changed considerably. Understanding these shifts is essential before approaching any lender.
Unlike standard residential borrowing, eight-figure mortgages rarely hinge on traditional income multiples. Instead, lenders focus on liquidity, asset profiles, global income, business ownership structures, and long-term banking relationships. Borrowers who understand these factors have a significantly higher success rate.
Willow Private Finance regularly supports high-net-worth (HNW) and ultra-high-net-worth (UHNW) clients with complex, multi-jurisdictional financial backgrounds. This includes borrowers with international income, offshore trusts, carried interest, or private equity distributions—areas where many mainstream brokers fail. Throughout this guide, we’ll explore how to approach lenders effectively and secure the most favourable terms.
For additional context on the broader lending environment, you may also find our articles on high-net-worth mortgages and private bank lending helpful.
The £5m–£20m lending space has become more competitive and selective in 2025. Rising base rates during the previous two years have encouraged private banks to refine their appetite for leverage, while also increasing the value of strong banking relationships.
At the same time, global wealth patterns have shifted. London continues to attract international buyers, particularly from Europe, the Middle East, and South-East Asia. This keeps demand for large mortgages high, increasing lender selectivity and tightening documentation requirements.
Affordability rules are different at this level. Most private banks now assess sustainability of income, liquidity buffers, and asset diversification rather than applying traditional stress tests. However, regulatory changes around source of wealth, AML checks, and income evidence have become more stringent, especially for overseas clients.
The trend toward bespoke underwriting has grown. Mortgages above £5m are almost never issued on a “product basis”—they are structured solutions, tailored to the client’s wider financial profile, investment strategy, and future plans.
A £5m–£20m mortgage can be structured in several ways, often with more flexibility than mainstream products. Most commonly, lenders deploy:
Interest-only structures, allowing borrowers to preserve liquidity and invest capital elsewhere. This is especially common for clients with investment portfolios, businesses, or carried interest.
Asset-backed lending, where the loan is supported by a combination of income, liquid assets, and enforceable guarantees. For example, private banks may take comfort from a diversified portfolio even if taxable income appears low.
Hybrid structures, blending interest-only with amortising components or offset facilities. These are increasingly popular for clients expecting future liquidity events.
Cross-collateralisation, where multiple assets—such as investment portfolios, global real estate, or corporate holdings—are used to strengthen the underwriting case.
These structures require negotiation and positioning. The strength of the borrower’s advisory team is often just as important as the borrower’s own credentials.
Lenders offering £5m–£20m mortgages operate with criteria far beyond standard underwriting. While each institution has its own nuances, several common themes dominate:
1. Demonstrable Liquidity
Private banks typically want borrowers to maintain a cushion of cash or near-cash assets. This can include portfolio holdings, retained profits, or corporate cash reserves. A liquidity buffer equal to 12–36 months of mortgage payments is common.
2. Global, Sustainable Income
Traditional income multiples are largely irrelevant. Instead, lenders look at the sustainability and predictability of:
Borrowers with variable income may need a multi-year track record or projections from accountants.
3. Strong Asset Base
Lenders want to see a diversified balance sheet—property, equities, business assets, and liquidity. This reduces reliance on any single income stream.
4. Transparent Source of Wealth
AML rules have tightened, requiring clear documentation for capital accumulation, business exits, inheritance, and global transfers.
5. Clean Corporate and Personal Structures
For clients using trusts, offshore companies, or multiple operating entities, clarity and documentation are essential. Weak structuring can slow approvals.
Borrowers seeking £5m–£20m in mortgage funding often face obstacles not present in mainstream lending. These include:
Complex Income Structures
Entrepreneurs and investment professionals often have income that is irregular, international, or realised through distributions. Many mainstream lenders are unequipped to assess this properly.
Cross-border Issues
Currency risk, tax residency, and documentation from multiple jurisdictions can complicate affordability assessments.
Private Bank Misalignment
Private banks frequently require assets under management (AUM). Some borrowers do not wish to transfer large portfolios or restructure investments.
Time Sensitivity
High-value transactions—especially in Prime Central London—often involve deadlines. Delays caused by compliance, valuations, or indicative terms can cost buyers opportunities.
Valuation Gaps
Luxury properties sometimes receive conservative valuations due to comparables, refurbishment needs, or market opacity. This can necessitate restructuring the lending request.
Borrowers who achieve the best outcomes follow strategies designed to align their financial profile with lender expectations. Key approaches include:
Presenting a Holistic Financial Profile
Private banks evaluate the bigger picture: assets, liabilities, global income, liquidity, and long-term wealth trajectory. A well-presented financial pack significantly speeds up underwriting.
Leveraging Assets Under Management
Some borrowers are willing to place AUM with a private bank to unlock preferential rates or higher LTVs. Others prefer to negotiate limited mandates or hybrid arrangements.
Using Future Liquidity Events
Upcoming bonuses, carried interest releases, business sales, or inheritance can be used to structure part-repayment plans, interest-only periods, or staggered amortisation.
Employing Multiple Entities
Trusts, SPVs, partnerships, and corporate structures can be used to optimise tax, ownership, and risk. Clear documentation is essential.
Securing Pre-Valuation Guidance
For large or unique properties, pre-valuation advice can help avoid surprise shortfalls. Willow frequently coordinates this for clients purchasing super-prime assets.
A typical £5m–£20m mortgage might involve:
In one generalised scenario, a private equity partner purchasing a £12m London townhouse secured a 65% LTV mortgage by demonstrating predictable carried interest and maintaining a seven-figure liquidity reserve. The bank structured a hybrid facility linked to future distributions, allowing flexibility without large AUM transfers.
In another scenario, an entrepreneur refinanced a £7m family home using a combination of retained profits, offshore assets, and company liquidity. The lender accepted a bespoke affordability model based on forward projections rather than traditional salary evidence.
These examples illustrate the flexibility available—but only when a case is positioned strategically.
As regulation tightens and global wealth becomes increasingly mobile, lenders will continue to refine their approach to high-value mortgages. Increasingly, the value placed on advisory expertise will grow—borrowers who approach lenders directly or without preparation risk being declined unnecessarily.
Over the next year, we expect:
Borrowers prepared to document their finances clearly, engage with specialist advisers, and approach the right lenders will continue to secure excellent outcomes.
Willow Private Finance specialises in large-value and complex lending, supporting clients across the UK and internationally. Our team regularly arranges £5m–£20m mortgages for entrepreneurs, executives, private equity partners, and UHNW families who require bespoke structuring and specialist underwriting.
We work with private banks, international lenders, and specialist institutions not available through mainstream channels. Our expertise lies in presenting complex financial profiles in a way that aligns with lender expectations—particularly when income is irregular, multi-jurisdictional, or asset-driven.
Whether you are purchasing, refinancing, or restructuring your wider wealth plan, our experience ensures you access the most competitive terms available.
Q1: What deposit do I need for a £5m–£20m mortgage in 2025?
A: Most private banks lend up to 60–70% LTV depending on liquidity, income stability, and asset profile. Larger loans may require additional collateral or AUM commitments.
Q2: Can I use international income to support a high-value mortgage?
A: Yes. Many lenders accept foreign income with proper documentation. Currency risk and sustainability will be assessed carefully.
Q3: Do private banks require assets under management (AUM)?
A: Some do, some don’t. AUM can unlock better rates or higher LTVs but is not always mandatory—especially when the borrower has strong liquidity.
Q4: How long does approval take for a large mortgage?
A: Typically 4–10 weeks depending on complexity, documentation, valuation schedules, and compliance reviews.
Q5: Can interest-only terms be negotiated on £5m–£20m mortgages?
A: Yes. Most large-value mortgages include interest-only or hybrid structures, especially when borrowers have future liquidity events.
Q6: Will lenders accept bonus or carried interest income?
A: Yes. Many private banks are familiar with investment-sector income and assess multi-year track records rather than a single year’s data.
Book a free strategy call with one of our mortgage specialists.
We’ll help you find the smartest way forward—whatever rates do next.
About the Author
Wesley Ranger is the Director of Willow Private Finance and has over 20 years of experience arranging complex, high-value, and international mortgage solutions. His expertise spans private banking, specialist lending, portfolio structuring, and strategic wealth-backed borrowing. Wesley has supported HNW and UHNW clients globally, helping them secure large property acquisitions, optimise leverage, and navigate multi-jurisdictional financial arrangements.
Important Notice
This article is for general information purposes only and does not constitute personal financial advice. Large-value mortgage lending is highly specialised, and product availability, eligibility, and rates vary based on individual circumstances, financial profiles, global income structures, and regulatory requirements. Requirements for AML, source of wealth, and compliance checks may change at any time.
Always seek tailored advice before committing to any financial arrangement.
Willow Private Finance Ltd is authorised and regulated by the Financial Conduct Authority (FCA No. 588422).
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