Mirror Wills & Joint Wills
Mirror wills and joint wills
Written by Eliza Elliott, Legacy Adviser at Octopus Legacy. Last updated: March 2026.
If you're making a will as a couple, you've probably come across the terms "mirror will," "joint will," and "mutual will." They sound similar but mean different things — and choosing the wrong one could leave your family unprotected.
This guide explains the differences, the risks, and which option is likely to work best for you.
What is a mirror will?
A mirror will is one of a pair of wills made by two people — usually spouses or partners — where the terms are essentially the same. Each person writes their own separate will, but the content mirrors the other.
For example, both wills might say: "I leave everything to my partner. If my partner has already died, I leave everything to our children equally."
The key point is that mirror wills are two separate legal documents. Each person owns their own will and can change or revoke it at any time — without needing the other person's permission.
When do mirror wills work well?
Mirror wills work well when you and your partner are on the same page. They're a good fit if:
- You want to leave everything to each other first, then to your children
- You share the same beneficiaries
- Your financial situation is straightforward
- You're in your first marriage with shared children
The risk of mirror wills
The biggest risk is what happens after the first death. Because mirror wills aren't legally binding on the survivor, the remaining partner can change their will at any time.
This creates a risk called sideways disinheritance. If the surviving partner remarries, their new spouse could inherit everything — and the children from the first relationship could end up with nothing. Marriage automatically revokes a will in England and Wales, so even without deliberate changes, remarriage could undo the original plan entirely.
This risk is especially important for blended families or second marriages.
What is a mutual will?
A mutual will looks like a mirror will but has one crucial difference: both people agree not to change the will after the first death. This agreement is legally binding.
Once one person dies, the surviving partner can't alter their will to change the beneficiaries. If they try to make a new will, it can be challenged and overturned.
Why are mutual wills less common?
Mutual wills are rare because they're inflexible. Life changes — people remarry, relationships shift, new children arrive, financial situations evolve. A mutual will locks you into decisions that may not make sense years later.
Most solicitors recommend mirror wills or wills with trusts over mutual wills for this reason.
What is a joint will?
In everyday language, "joint wills" usually just means two people writing their wills at the same time — as two separate documents. It doesn't mean a single shared document.
True joint wills (one document covering two people) are extremely rare in England and Wales and are generally discouraged by solicitors. They create legal complications and are difficult to administer after the first death.
When people say "joint wills," they typically mean what we'd call writing your wills together as a couple — two individual wills created side by side.
Mirror wills vs separate wills: which is better?
The distinction between "mirror wills" and "separate wills for couples" is smaller than you might think. In both cases, each person has their own legal document. The difference is how much the content matches.
| Feature | Mirror wills | Separate wills (written together) |
|---|---|---|
| Number of documents | Two (one each) | Two (one each) |
| Content | Identical or near-identical | Can match in some areas, differ in others |
| Can be changed independently? | Yes | Yes |
| Good for blended families? | Not always — doesn't account for children from different relationships | Yes — each person can name their own beneficiaries |
| Flexibility | Limited (same content for both) | Full flexibility per person |
| Funeral wishes | Must be the same | Can be different |
| Charity donations | Must match | Each person can choose their own |
For most modern couples, writing individual wills together gives you the best of both worlds. You can match the things that matter — like guardians for your children or how the estate is divided — while keeping the freedom to personalise the rest.
Tax implications of mirror wills
Mirror wills don't create special tax advantages on their own. But the way you structure your will as a couple has a direct impact on how much inheritance tax your family pays.
Spouse exemption
Assets passed between married couples or civil partners are exempt from inheritance tax. This means the first death usually triggers no IHT at all if everything passes to the surviving spouse.
Transferable nil-rate bands
When the first spouse dies and their nil-rate band isn't fully used, the unused portion transfers to the surviving spouse's estate. This means the second estate can benefit from:
- Up to £650,000 combined nil-rate band (2 × £325,000)
- Up to £350,000 combined residence nil-rate band (2 × £175,000) — if the home passes to direct descendants
- A combined maximum threshold of £1,000,000 before IHT is due
Both thresholds are frozen until April 2030.
When mirror wills aren't tax-efficient
Leaving everything to your spouse is simple, but it's not always the most tax-efficient approach. If the surviving spouse's estate grows significantly — through inheritance, property value increases, or pension changes — it could push the total above the combined thresholds.
From April 2027, unused pension pots will be included in estates for IHT purposes. This could affect couples who've been relying on the pension exemption.
For larger estates, a will with a trust can protect assets while still providing for the surviving spouse. This is something to discuss with a professional adviser.
Protecting against sideways disinheritance
If you're worried about what happens if your partner remarries after your death, there are options:
Life interest trust (right to reside trust)
Your share of the home is held in trust for your children, but your partner has the right to live in it for the rest of their life. When they die or move out, your share passes to your children as intended.
Property protection trust
Similar to a life interest trust but specifically designed to ring-fence your share of a jointly owned property. It prevents your share being absorbed into the surviving partner's estate.
These trusts need careful drafting. Octopus Legacy offers wills with trusts starting from £450 for one person or £750 for a couple.
What should couples include in their wills?
Whether you choose mirror wills or separate wills, here are the key things to think about:
- Executors — who will carry out your wishes? You might name each other, with a backup.
- Guardians for children — who looks after your children if you both die? This is one area where matching makes sense.
- Pet guardians — who takes care of any pets?
- How the estate is divided — do you want everything to go to each other first, then children? Or do you want specific gifts?
- Trusts — do you need a trust to protect property or provide for children from a previous relationship?
- Funeral wishes — these can be different for each person
- Charity donations — each person can choose their own causes
- Lasting power of attorney — not part of the will, but something every couple should set up at the same time
How much do wills for couples cost with Octopus Legacy?
| Will type | One person | Couple / mirror wills |
|---|---|---|
| Simple will | £150 | £250 |
| Will with trust | £450 | £750 |
With Octopus Legacy, each person has their own account. You can match each other's wishes where you want to and personalise the rest. You can update your own will at any time — without affecting your partner's.
Our wills are available online, by video call, or in person. Every will is checked by our team before it's finalised.
Write your will with Octopus Legacy →
What is a mirror will?
A mirror will is one of a pair of wills made by two people where the terms are essentially the same. Each person has their own separate document, but the content mirrors the other. Both might leave everything to the surviving partner first, then to children equally.
What is the difference between a mirror will and a mutual will?
Mirror wills can be changed by either person at any time. Mutual wills include a legally binding agreement that neither person will change the will after the first death. Mutual wills are rare because they can't accommodate life changes.
Can a mirror will be changed after one person dies?
Yes. Mirror wills aren't legally binding on the survivor. The remaining partner can change their will at any time. This is a key risk — the original beneficiaries could be disinherited if the survivor changes their will or remarries.
What is sideways disinheritance?
It happens when the surviving partner remarries or changes their will, and children from the first relationship inherit nothing. Marriage automatically revokes a will in England and Wales, so remarriage alone could undo the original plan.
Do mirror wills save on inheritance tax?
Not on their own. But assets between married couples are exempt from IHT. When the first spouse dies, any unused nil-rate band transfers to the survivor. This gives a combined threshold of up to £1,000,000 for qualifying estates (£650,000 NRB + £350,000 RNRB).
How much do mirror wills cost with Octopus Legacy?
Simple wills cost £150 for one person or £250 for a couple. Wills with trust cost £450 for one person or £750 for a couple. Available online, by video call, or in person. Each person has their own account and can update independently.
Should couples get mirror wills or separate wills?
For most couples, writing individual wills together is best. You can match the important things — guardians, estate division — while personalising the rest. This matters most for blended families or couples with children from previous relationships.
What is a life interest trust and when do couples need one?
A trust that holds your share of a property for your children, while your partner keeps the right to live there. It protects against sideways disinheritance. Especially useful for blended families or second marriages.
