A standard will hands your children the lot at 18. Here is when that matters.

Most parents who write a standard will assume their children get the money 'when they are old enough' or 'when the time is right'. They do not. Under a standard will, and under the intestacy rules if there is no will at all, children inherit their share outright the moment they reach the age of majority.

In England, Wales and Northern Ireland that age is 18. In Scotland it is 16. There is no automatic mechanism in a standard will that holds back the inheritance, lets a trusted adult release it gradually, or protects it from how an 18-year-old's life is actually going at that moment.

For some families, an 18-year-old (or 16-year-old in Scotland) receiving a modest inheritance is genuinely fine. For others, it is the single most avoidable problem with their current will.

What 'inherit outright at 18' actually means

On the child's 18th birthday (or 16th in Scotland), the executor or trustee of the will is legally required to transfer the child's share of the estate into their hands. That can include:

• The cash proceeds of a sold property
• Investment portfolios and ISAs
• Life insurance proceeds payable into the estate
• Their share of any other estate asset

From that day, they are the legal owner. How they spend, invest, gift, lend or lose the money is no longer something a parent, guardian or trustee can override.

If both parents in a family with two young children die in an accident with an estate of, say, £600,000, the children may each inherit around £300,000 at 18. That is rarely the picture parents have in mind when they sign a standard will leaving 'everything to my children equally'.

Four situations where the age-18 rule really matters

1. Young children who would inherit a large sum

A young child today is 18 in well under twenty years. Combine a typical UK home, some pension life cover and a modest second-property or investment account, and the sum landing on an 18-year-old can quickly run into six figures. That is enough to derail education, distort relationships, or be lost to a poor decision before any real adult judgement has had time to develop.

2. Blended families and second marriages

When children from an earlier relationship are involved, or where stepchildren and biological children mix, leaving everything outright to a surviving partner risks the inheritance disappearing if that partner remarries or rewrites their own will. Leaving everything outright to children at 18 brings its own problems. A trust within the will, often a life interest trust for the partner with the capital preserved for named children, sits between these two unattractive outcomes.

3. A vulnerable or disabled beneficiary

Where a child has a disability, a long-term mental health condition or any other reason their financial decisions could be a real concern in adulthood, an outright inheritance at 18 can also put means-tested benefits at risk. A discretionary trust written into the will lets trustees release funds in ways that support the beneficiary without prejudicing those entitlements. The same logic applies to an adult child whose circumstances are precarious, even if they are well over 18 at the date of death.

4. Protecting an inheritance from a future divorce or creditors

Once an inheritance is in a child's own name, it can become part of the matrimonial pot in a future divorce or be exposed to a future creditor claim. Holding the inheritance in trust does not give absolute protection, but assets held in a properly drafted discretionary trust are generally treated very differently from assets held outright. For families where a child is in (or may enter) a business or a difficult marriage, this can be the most valuable feature of the trust.

How a trust in the will solves it

A trust written into the will (a 'testamentary trust') does not exist until you die. When it does, named trustees hold the child's share and release funds on terms you have set out: at a specified later age (say 25 or 30, or in stages), or at the trustees' discretion based on the child's needs and circumstances.

The common structures are discretionary trusts, where trustees decide who benefits and how, and age-contingent absolute trusts, where the share is held until a fixed age. The right structure depends on the family. Both are well-trodden ground for a solicitor drafting wills properly.

How this differs from a lifetime 'family trust'

A trust written into a will is not the same as a separate lifetime family trust. You do not register it with HMRC's Trust Registration Service while you are alive, you do not start a 7-year clock during your lifetime, and you do not lose access to any of your assets now. It is simply a set of instructions in the will that activates on death.

Because of that, building a trust into the will tends to add only a modest amount to the cost of a will compared with setting up a standalone lifetime trust deed. It is one of the higher-value upgrades a will writer can offer.

The decision in one question

If you and your partner died together this year, are you comfortable that the youngest beneficiary receiving their share in cash on their 18th birthday (or 16th, in Scotland) is the outcome you want? If the answer is no, a trust in your will is the missing piece.

Simply Estate is an estate planning firm. Our team can build a trust into your will at the right level for your family, without selling you a standalone trust you do not need. Visit our trusts page to book your free, no-obligation review.