Sideways Disinheritance UK: How to Protect Your Children
Sideways disinheritance is one of the most common ways families are unintentionally cut out of an inheritance. It happens when a surviving spouse remarries — and their new partner ends up with everything. Here is how it works and how to stop it.
What Is Sideways Disinheritance?
The term describes a situation where children from a first marriage or relationship are ultimately disinherited — not because their parent chose to cut them out, but because events after their parent’s death removed the assets from the family.
The classic sequence is:
- Husband and wife make mirror wills leaving everything to each other, then to their children equally.
- Husband dies. Wife inherits everything outright — as planned.
- Wife remarries. Under English law, marriage automatically revokes a will (unless the will was made in contemplation of that marriage).
- Wife dies without making a new will — or makes a new will leaving everything to her new husband.
- The children of the first marriage receive nothing.
Even without remarriage, sideways disinheritance can occur if a surviving spouse simply falls out with their children, forms a new relationship (without marrying), or falls into financial difficulty — meaning the assets intended for the next generation are spent or redirected.
With nearly one in three marriages in England and Wales ending in divorce, and significant numbers of widowed people remarrying in later life, this is not a rare edge case. It is one of the most common estate planning failures solicitors encounter.
Why Mirror Wills Do Not Protect Your Children
Mirror wills are two separate documents — one for each spouse — that mirror each other in content. They are not a contract. When the first spouse dies, their will is spent. The surviving spouse holds everything outright, as if no will had been made at all in their favour. They are completely free to:
- Make a new will leaving everything to a new partner
- Marry again (automatically revoking their existing will)
- Gift assets away during their lifetime
- Spend the assets on care fees, gifts, or other purposes
Mirror wills are perfectly suitable for most couples with no children from previous relationships and no particular reason to fear the above scenarios. For blended families or where asset protection for children is a priority, they are inadequate.
Solutions: How to Prevent Sideways Disinheritance
1. Life Interest Trust (Property Protection Trust)
The most widely used solution. Instead of leaving your share of the matrimonial home (or other assets) outright to your spouse, you leave it to a trust. The surviving spouse has the right to live in the property for life (or receive the income from the trust assets), but the capital is ring-fenced for your children or other beneficiaries.
When the surviving spouse dies — whether they have remarried or not — the capital passes to your chosen remainder beneficiaries as the trust dictates. A new will by the surviving spouse cannot touch it.
2. Flexible Life Interest Trust
A more adaptable version of the life interest trust. The trustees (who you appoint in your will) have discretion to advance capital to the surviving spouse in genuine need — for example, care home fees, major medical costs, or urgent repairs to the property. This flexibility reduces the rigidity of a basic life interest trust without sacrificing the protection.
Flexible life interest trusts are increasingly the default recommendation from estate planning solicitors precisely because they can respond to changing circumstances over what might be a 20-year trust period.
3. Discretionary Testamentary Trust
For larger estates or more complex family situations, all or part of the estate can pass into a discretionary trust rather than to the surviving spouse outright. The trustees — who can include the surviving spouse — have full discretion to distribute income and capital among a defined class of beneficiaries (typically spouse and children). No beneficiary has a fixed entitlement, which provides maximum flexibility but requires trusted, competent trustees and professional management.
4. Life Insurance for Children Written in Trust
An immediate safeguard: take out a life insurance policy and write it in trust for your children directly. On your death the policy pays out to the trust, bypassing your estate entirely. This means even if your spouse later redirects your estate, your children receive a guaranteed sum. Premiums can be modest for younger, healthier people and the policy does not affect IHT or probate.
5. Mutual Wills (Use with Caution)
Mutual wills are a formal contract between two people that their wills will not be changed after the first death. The survivor is bound by the arrangement for the rest of their life. While legally enforceable, mutual wills are rarely recommended because they bind the survivor inflexibly for decades, regardless of changing tax law, circumstances, or needs. Life interest trusts achieve the same protective outcome with far more flexibility.
Comparing the Solutions at a Glance
| Solution | Protection level | Flexibility | Complexity |
|---|---|---|---|
| Mirror wills only | None | High | Low |
| Life interest trust | High — capital protected | Medium | Medium |
| Flexible life interest trust | High + adaptable | High | Medium-high |
| Life insurance in trust | Partial — only for insured amount | High | Low |
| Mutual wills | High — but inflexible | Very low | Medium |
Steps to Take Now
Review your existing will
Does it leave everything outright to your spouse? If so, you have no sideways disinheritance protection. Check whether a trust-based will would be more appropriate for your family circumstances.
Identify the at-risk assets
Typically the matrimonial home and any significant savings or investments. These are the assets most likely to be redirected in a second marriage scenario.
Talk to your spouse or partner
Sideways disinheritance protection works best when both partners are aligned. A life interest trust requires your spouse to accept that the capital will ultimately go to your children — this should be an honest conversation, not a surprise.
Update your will
If you have a straightforward estate and want simple protection, a WillSafe will kit can include trust provisions. For complex blended family arrangements, a solicitor who specialises in trusts and estates will tailor the arrangement.
Review after any major life change
Separation, divorce, a new relationship, or the death of a beneficiary all require a will review. Do not rely on an old mirror will made before your family circumstances changed.
Frequently Asked Questions
Can I force my surviving spouse not to change their will after I die?
Not directly. If you leave everything to your spouse outright, they are the absolute owner and can do whatever they wish with it — including writing a new will leaving it all to a new partner. The only way to bind a surviving spouse is through mutual wills (a legally enforceable agreement not to change the will) or, more commonly, by using a life interest trust rather than outright gifts. A life interest trust gives the survivor the use or income of the assets for life but passes the capital to your chosen beneficiaries — usually your children — on the survivor's death. The survivor cannot revoke this arrangement.
What is the difference between a life interest trust and a flexible life interest trust for sideways disinheritance protection?
A basic life interest trust gives the surviving spouse a fixed right to income or occupation — for example, the right to live in the matrimonial home for life. They cannot access the capital. A flexible life interest trust gives the trustees discretionary power to advance capital to the life tenant in case of genuine need (e.g. care home fees, major medical costs) while still preserving the remainder for your children. The flexible version is generally preferred because it gives your trustees the ability to respond to unforeseen circumstances rather than being rigidly bound. Both types protect against sideways disinheritance by ensuring the capital ultimately passes to your intended beneficiaries.
Can my children make an inheritance claim if they are disinherited sideways?
Possibly, but the bar is high. Under the Inheritance (Provision for Family and Dependants) Act 1975, an adult child can apply to the court for reasonable financial provision from a deceased parent's estate — but 'reasonable provision' for an adult child is limited to what is needed for their maintenance. Courts are reluctant to make substantial awards to adult children who are financially independent. The claim must be made within six months of the grant of probate. By then, the estate may already have been distributed and the assets passed to a new spouse. Prevention is far more reliable than remedy.
Are mutual wills a reliable way to prevent sideways disinheritance?
Mutual wills are a formal agreement between two people that their wills will not be changed after the first death, creating a constructive trust that binds the survivor. They are legally recognised in England and Wales but rarely recommended. Problems include: (1) the survivor is bound for the rest of their life, even if circumstances change substantially; (2) the doctrine can be difficult to enforce if the agreement was oral or vague; (3) the survivor cannot even benefit from a deed of variation after the first death; (4) changed legislation or tax rules may make the arrangement harmful. Life interest trusts are almost always preferable — they protect the capital for your beneficiaries without binding the survivor's freedom in the same blanket way.
Does a life interest trust affect inheritance tax when the surviving spouse dies?
Yes. Where the life interest trust is an Immediate Post-Death Interest (IPDI) — which most spousal life interest trusts are — the assets in the trust are treated as part of the life tenant's estate for inheritance tax on their death, even though they do not own them outright. This means the surviving spouse's nil-rate band and residence nil-rate band (where applicable) are available against the trust fund. Critically, the unused nil-rate band of the first spouse to die is transferable to the survivor, so up to £650,000 (or £1 million with RNRB) can pass free of IHT. On the life tenant's death, the capital then passes to the remainder beneficiaries (your children) under the trust — not as part of the survivor's estate for distribution purposes.
Make Sure Your Children Are Protected
A clearly drafted will with the right trust provisions protects your children from sideways disinheritance — however your surviving spouse’s circumstances change after your death.