The Bank of Mum and Dad is now one of the largest sources of housing finance in the United Kingdom. Estimates from Legal & General consistently place family-funded deposits in the billions annually, making parental lending a force that rivals some mid-tier mortgage providers. Yet most of these transactions are sealed with nothing more than a verbal promise and a vague understanding that “we’ll sort it out later.” That casualness is a ticking time bomb — and a new wave of fintech platforms is attempting to defuse it.
If you are lending to, or borrowing from, a family member to buy property, you need to understand what is actually at stake. The sums involved have grown far beyond the point where informality is acceptable. And the legal, tax, and relationship consequences of getting this wrong are severe.
Why Informal Family Loans Are So Dangerous
The core problem is simple: most families treat a £50,000 gift or loan the same way they would treat lending someone a tenner. No written terms, no repayment schedule, no clarity on whether the money is a gift or a loan, and no understanding of what happens if things go wrong. This creates at least four serious risks.
Mortgage lender scrutiny
Every mainstream UK mortgage lender will ask where a deposit came from. If the money is a gift, lenders require a signed gifted deposit letter confirming no repayment is expected. If it is a loan, most lenders will factor the repayments into affordability calculations — and many will decline the application outright. Families that fudge this distinction are committing mortgage fraud, full stop. It does not matter that no one “intended” to deceive anyone.
Inheritance tax exposure
If a parent gives a large sum and dies within seven years, the gift may be subject to inheritance tax under the failed potentially exempt transfer (PET) rules. A loan avoids this problem because the capital remains part of the lender’s estate — but only if it genuinely is a loan, with documented terms and actual repayments being made. HMRC will look at substance over form. An undocumented “loan” with no repayments looks, to a tax inspector, exactly like a gift.
Relationship breakdown
If the borrower divorces or separates from a partner, undocumented family money is notoriously difficult to protect. A family court may treat it as a gift to the couple rather than a loan to one party. Without a formal loan agreement — ideally executed as a deed, which carries a twelve-year limitation period rather than six — the lending parents may have no enforceable claim at all.
Capital gains tax surprises
Where a parent takes a beneficial interest in the property (rather than simply lending money), CGT becomes relevant. Principal private residence relief only applies to the portion of the property that is the owner’s actual main home. A parent who holds a share but lives elsewhere has no PPR relief on their portion, meaning a sale could trigger a meaningful tax bill.
What the New Fintech Platforms Actually Do
A growing number of UK and international fintech tools now aim to formalise family lending. At their best, these platforms convert a handshake into a structured, documented arrangement. Typical features include templated loan agreements, automated repayment tracking, payment reminders, and dashboards showing outstanding balances.
This is genuinely useful. Automated tracking removes the single most corrosive element of family lending — the awkward “have you forgotten about the money?” conversation. A platform that sends a neutral payment reminder is vastly preferable to a parent having to chase their own child.
However, you need to understand the limits. A templated loan agreement generated by an app is better than nothing, but it is not a substitute for proper legal advice in every situation. Specifically, if the family loan is connected to a property purchase, you almost certainly need a solicitor to address the following:
- Declaration of Trust: If the parent takes a beneficial interest in the property rather than simply lending money, a Declaration of Trust (also called a Deed of Trust) is essential. This document specifies ownership percentages, what happens on sale, and whether unequal contributions are treated as loans or equity. Without it, the default legal presumption for joint owners is equal shares — regardless of who actually paid what.
- Tenancy in common versus joint tenancy: If a parent is going on the title, tenancy in common is almost always the correct structure. It allows unequal shares and independent inheritance rights. Joint tenancy triggers automatic survivorship — meaning if one owner dies, their share passes to the other owner by operation of law, potentially overriding their will entirely.
- SDLT surcharge: This catches families off guard constantly. If a parent is added to the title and they already own property — including their own home — the three per cent SDLT higher rate applies to the entire purchase price. On a £300,000 property, that is an additional £9,000. This applies even if the child is a first-time buyer.
- TOLATA 1996: Under the Trusts of Land and Appointment of Trustees Act, any co-owner can apply to court to force a sale of the property even if the other party objects. If your family arrangement involves co-ownership, you need to understand that this nuclear option exists.
The Borrower’s Future Mortgage Capacity
One issue that fintech platforms rarely highlight is the impact on future borrowing. If a family loan is properly disclosed to a mortgage lender — as it must be — the repayments reduce the borrower’s affordability. More critically, if a parent is named on the mortgage itself (as in a joint borrower sole proprietor arrangement), lenders will stress-test that parent against the full mortgage debt when assessing any future application they make. A parent who helps a child buy a flat may find they cannot remortgage their own home or downsize without complications.
What a Proper Family Loan Agreement Should Include
Whether you use a fintech platform or a solicitor — ideally both — your agreement needs these elements at minimum:
- The exact amount lent and the date of the advance.
- Whether interest is charged, and if so, the rate and basis (noting that HMRC may impute a commercial rate for tax purposes if interest is artificially low or absent on very large sums).
- A repayment schedule with specific dates and amounts.
- What happens on default — grace periods, accelerated repayment triggers, and whether the loan is secured against any asset.
- What happens if the borrower sells the property, dies, or enters bankruptcy.
- Explicit confirmation that the sum is a loan, not a gift, to protect both sides in family court proceedings or HMRC enquiries.
- Execution as a deed, with independent witnesses, to secure the twelve-year limitation period.
The Bottom Line
Fintech platforms that bring structure to family lending are a welcome development — they lower the friction of doing what everyone should have been doing all along. But technology is a tool, not a shield. If your family is lending or borrowing five or six figures to support a property purchase, a templated app agreement is the starting point, not the finish line. Spend the money on a solicitor who understands co-ownership, a properly drafted Declaration of Trust, and — if the parent is going on the title — a clear-eyed conversation about SDLT, CGT, IHT, and future mortgage capacity. The Bank of Mum and Dad deserves the same rigour as any other lender. The people involved deserve considerably more care.
Disclaimer: The information provided in this article is for informational purposes only and should not be considered financial or legal advice. Property and lending laws in the United Kingdom vary and may change over time. We always recommend consulting with a qualified solicitor and mortgage broker before entering into a property purchase or financial arrangement with another party.
