Every year, hundreds of thousands of UK parents dip into savings, pensions, or property equity to help their children buy a home. By some estimates, the so-called Bank of Mum and Dad would rank among the country’s top ten mortgage lenders if it were a real institution. With average house prices in England sitting above £290,000 and first-time buyer deposits routinely exceeding £50,000, the impulse to help is entirely understandable. But the way most families structure that help — a vague gift, a handshake loan, a hastily arranged transfer with no paperwork — is where the real damage is done. In 2026, tightening tax rules, elevated stamp duty thresholds, and a volatile housing market make it more important than ever to get this right. Here is why winging it could cost your family thousands, and what to do instead.
Joint and Several Liability: The Fact Almost Everyone Gets Wrong
When parents go beyond gifting a deposit and instead join the mortgage as a co-buyer, they expose themselves to a risk most families catastrophically underestimate. On a joint mortgage, each borrower is liable for one hundred per cent of the debt — not half, not their “fair share,” the entire balance. If your child stops paying, the lender will not politely ask for your fifty per cent. They will pursue whichever borrower has the money, and that is usually the parent with a pension pot and a paid-off home.
Worse still, that mortgage will appear on your credit file and reduce your future borrowing capacity. Lenders stress-test each borrower against the full outstanding mortgage debt when assessing new applications. If you planned to remortgage your own property, help another child, or release equity in retirement, you may find yourself locked out. The commitment does not quietly sit in the background — it actively constrains your financial life for decades.
The SDLT Surcharge Trap
Stamp Duty Land Tax catches families off guard with brutal regularity. If either co-buyer already owns property — anywhere in the world — the 3% SDLT higher rate applies to the entire purchase price, not just one person’s share. A parent who owns their family home joining a child’s £350,000 purchase as a co-buyer would trigger an additional £10,500 in SDLT. That is money burned before anyone picks up the keys, and it comes as an unwelcome surprise at completion because solicitors sometimes assume clients already know.
Even if the parent is not on the mortgage but holds a beneficial interest in the property through a poorly drafted arrangement, HMRC may still argue the surcharge applies. This is one area where taking advice before exchange — not after — is non-negotiable.
Gifts, Loans, and the Seven-Year Inheritance Tax Clock
Many parents treat a deposit contribution as a straightforward gift. Emotionally, it often is. Legally and fiscally, it is anything but. A gift above the annual exemption counts as a Potentially Exempt Transfer for Inheritance Tax purposes. If the parent dies within seven years, the gift falls back into their estate, potentially triggering a 40% IHT charge on the amount above the nil-rate band. With the nil-rate band frozen at £325,000 until at least 2028, and house prices pushing more estates over that threshold, this is not a theoretical risk — it is a live one.
Structuring the contribution as a formal loan changes the picture. A loan remains an asset in the parent’s estate (which does not help with IHT on its own), but it can be forgiven gradually through annual exempt gifts of £3,000, used strategically alongside normal-expenditure-out-of-income exemptions, or repaid to keep the capital within the parent’s control. The key point: a loan preserves options. A gift is irrevocable.
Relationship Breakdown and the Missing Declaration of Trust
Roughly 42% of marriages in England and Wales end in divorce. Cohabiting relationships break down even more frequently, and cohabitants have far fewer automatic legal protections. When parents gift money for a deposit and their child’s relationship later ends, that money enters the pot available for division — whether the couple were married or not, if the property was held jointly.
A Declaration of Trust (also called a Deed of Trust) is the single most important document most co-owning families never bother to create. It records each party’s beneficial interest, specifies what happens on sale, and clarifies whether unequal contributions are treated as loans to be repaid or equity adjustments that shift ownership percentages. Without one, the default legal position is often equal shares regardless of who actually paid what. Courts and HMRC will not reconstruct your family’s good intentions from memory.
Because a Declaration of Trust is executed as a deed, it carries a twelve-year limitation period for enforcement — double the six years you get with a standard contract. If you are going to put something in writing, make it a deed.
Tenancy in Common: The Only Sensible Structure for Non-Married Co-Owners
Property can be held as either a joint tenancy or a tenancy in common. Under a joint tenancy, when one owner dies their share passes automatically to the surviving owner — regardless of what their will says. This is fine for married couples. For a parent and child, or siblings buying together, it is almost always wrong.
A tenancy in common allows unequal shares, independent inheritance rights, and no forced survivorship. Each owner can leave their share to whomever they choose. If a parent has contributed 40% of the purchase price, a tenancy in common lets them hold 40%, protect that interest in their will, and ensure it passes to the right people. Register the tenancy in common with HM Land Registry by filing a Form A restriction — this prevents a sale without all owners’ consent and puts the world on notice of the arrangement.
TOLATA: The Nuclear Option Nobody Expects
Under the Trusts of Land and Appointment of Trustees Act 1996, either co-owner can apply to court to force a sale of the property, even if the other party refuses. This is the litigation risk that most family arrangements ignore entirely. If your child wants to sell and you do not — or vice versa — TOLATA gives the aggrieved party a legal mechanism to compel it. Proceedings are expensive, emotionally devastating, and entirely avoidable with a properly drafted co-ownership agreement that includes a buy-sell mechanism, a right of first refusal, and a clear exit timeline.
Capital Gains Tax and Principal Private Residence Relief
If a parent is named as co-owner but does not live in the property, their share does not qualify for Principal Private Residence Relief on sale. Any gain attributable to the parent’s share is chargeable to CGT at 18% or 24% depending on their total taxable income. On a property that has appreciated by £100,000, a parent holding a 25% share could face a CGT bill exceeding £5,000. This is money families simply do not budget for because they assume the whole property is exempt.
What a Proper Co-Ownership Agreement Must Include
Whether money is gifted, lent, or used to purchase a share, the family needs a written co-ownership agreement covering at minimum:
- Beneficial interest percentages and how they adjust if one party pays more over time
- Right of first refusal if either party wants to sell their share
- Buy-sell mechanism with independent valuation procedure
- Exit timeline — how long must the other party be given to arrange finance or find a buyer
- Shared expense account for mortgage payments, insurance, and repairs
- Occupancy rules — who lives there, can it be let, what happens if someone moves out
- Renovation consent thresholds — spending above an agreed amount requires both parties’ approval
- Default provisions — what happens if one party stops paying their share
The Bottom Line
Helping your child buy a home is one of the most generous things you can do. But generosity without structure is reckless. Get a solicitor to draft a Declaration of Trust executed as a deed. Hold the property as tenants in common. Put a co-ownership agreement in place that covers exit, expense-sharing, and dispute resolution. If you are lending rather than gifting, document the terms formally — interest rate, repayment schedule, what happens on default. If you are gifting, understand the IHT clock and make sure your will accounts for it so your other children are not short-changed. The cost of proper legal advice is typically £1,000 to £2,500. The cost of getting it wrong can run to tens of thousands, family relationships included. Spend the money now.
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.
