"Joint will" and "mirror will" sound similar but mean very different things. A joint will is one document signed by two people. Mirror wills are two separate documents with matching contents. The difference matters at probate, after the first death, and for how easily either of you can change your mind later. This guide explains what each one is, when one beats the other, and why most UK couples in 2026 are better off with mirror wills than joint wills.
Key takeaways:
- Joint will = one document, two signatures. The same document covers both partners' estates. Becomes binding when the first partner dies.
- Mirror wills = two separate documents with matching contents. Each goes through probate independently when its testator dies.
- Joint wills are rare in modern UK practice because they cause probate complications and severely limit the surviving partner's flexibility.
- Mirror wills are far more common, easier to administer, and let each partner update their will independently.
- If you want the survivor to be legally bound to keep the agreement, look at mutual wills rather than a joint will.
What a joint will is
A joint will is a single legal document executed by two people, usually a married couple, covering both of their estates. Both partners sign, both have witnesses, and the document covers what happens to:
- The first partner to die's estate
- The surviving partner's estate when they eventually die
- Both estates together
The same document is presented at probate twice — once when the first partner dies, and again when the second partner dies. Between the two deaths, the surviving partner technically has the same document but cannot easily revoke or amend the parts dealing with the first partner's wishes.
What mirror wills are
Mirror wills are two separate wills, each signed by one partner, that contain matching wishes. The wills are legally independent: each one goes through probate independently, each can be amended independently, each can be revoked independently. They "mirror" each other in content but are not linked legally. See our mirror wills explained guide for the full picture.
The practical differences
| | Joint will | Mirror wills |
|---|---|---|
| Number of documents | 1 | 2 |
| Number of signatures | 2 (one per partner) | 2 (one each per will) |
| Number of witnesses | 2 (witnessing both signatures) | 2 per will (can be the same people, signed in same sitting) |
| What happens at first death | Document is admitted to probate; surviving partner's portion is "suspended" | First partner's will is admitted to probate; surviving partner's will is unaffected |
| Can the survivor change their wishes? | Difficult — joint wills carry an implication of mutual agreement that's harder to revoke | Yes, completely freely. The surviving partner's will is theirs to amend, revoke, or replace. |
| Cost | Similar to mirror wills | Trusted Hands: £179 for the pair |
| Common in modern UK practice? | Rare | Standard |
Why joint wills are rare in modern UK practice
Joint wills used to be more common in earlier eras when one document was simpler to draft and store. Today they are uncommon for three reasons:
1. Probate complications after the first death
When the first partner dies and the joint will is admitted to probate, the document is technically tied up with the executors of the first estate. Practical issues arise around storage, copying and access. Modern administration is significantly easier with two separate documents.
2. The surviving partner is constrained
Even though a joint will doesn't legally bind the survivor in the same way mutual wills do, courts have interpreted joint wills as carrying an implied agreement between the partners. A surviving partner who tries to substantially rewrite the joint document after the first death faces a higher hurdle of justification than a survivor with their own independent mirror will.
3. Updating is harder
If both partners are alive and want to amend their wishes, a new joint will needs both signatures and both sets of witnesses. With mirror wills, each partner can update their own will independently — much easier when circumstances change.
When a joint will might still make sense
The narrow case: a couple with completely identical wishes, no expected changes, no children from previous relationships, and a strong preference for a single legal document. Even then, mirror wills handle the same situation just as well with more flexibility.
When mirror wills are the right answer
Mirror wills are right for the vast majority of UK couples:
- Married, civil partners, or cohabiting couples
- Wishes that broadly match
- Wanting to be able to update your own will independently in future
- Wanting clean, straightforward probate after each death
- Same beneficiaries (typically the surviving partner first, then children)
- Same executor and guardian choices
If those describe you, mirror wills are the right answer.
When you should look at mutual wills instead
Mutual wills are a third option, sometimes confused with both joint and mirror wills. Mutual wills are two separate documents that legally bind each other. After the first partner dies, the surviving partner cannot rewrite their will to override the original agreement.
This is often the right answer for:
- Blended families where one partner has children from a previous relationship
- Couples worried that the survivor might remarry and disinherit the deceased's children
- Situations where the agreement between you is more important than future flexibility
The trade-off: mutual wills are inflexible. Once one partner has died, the survivor is locked in. See planning a will when remarrying for the trade-off in detail.
Trusted Hands recommends mirror wills for most couples and mutual wills for blended families. Both are built in the same guided online journey. Start mirror wills → or Start mutual wills →
How to choose
A simple decision tree:
- Do you and your partner have substantially similar wishes? No → consider two separate single wills.
- Do you both want to be able to update independently later? Yes → mirror wills.
- Do you both want to bind each other so the survivor can't change the agreement? Yes → mutual wills.
- Do you want one document covering both of you? Yes → joint will (but consider mirror wills first — they cover the same ground with fewer downsides).
Frequently asked questions
Is a joint will more legally binding than mirror wills?
Slightly, but only on the survivor and only by implication. Mirror wills are independent; the survivor can rewrite theirs freely. A joint will carries an implied mutual agreement that makes substantial rewrites harder to justify in court — but not impossible. For a genuinely binding agreement, use mutual wills, not a joint will.
Can a joint will be revoked?
While both partners are alive, yes — both have to sign a new will or formally revoke the joint will. After the first death, the surviving partner faces more difficulty than they would with a mirror will, but a court can still allow revocation in many circumstances.
Do mirror wills cost more than a joint will?
In modern practice, they cost about the same. Most online services don't even offer joint wills because the demand is low and mirror wills work better. Trusted Hands offers mirror wills (£179) and mutual wills (£199), but not joint wills.
What if one of us wants a joint will and the other wants mirror wills?
Talk it through — the discussion usually reveals you both want the same end result and just disagree on the form. Mirror wills cover what most "I want a joint will" couples actually want.
Can unmarried couples have joint wills?
Legally, yes — any two people can sign a joint will. In practice, it makes even less sense for unmarried couples than for spouses, because the implied agreement gets weaker without a marriage. Mirror wills or two single wills are usually the right answer.
What if our wishes differ slightly?
Mirror wills handle this fine. "Mirror" means the wills sit alongside each other, not that they must be identical down to the letter. You can each tailor your own will while keeping the broad structure the same.
Can I convert a joint will to mirror wills?
Yes, while both partners are alive. Sign two new individual wills (which automatically revoke the joint will if drafted correctly), and store them separately. Trusted Hands can build the mirror wills in the guided builder.
Trusted Hands is a UK will-writing service, not a firm of solicitors. For most couples, mirror wills are the right answer; for blended families consider mutual wills; for complex estates, regulated legal advice is appropriate.
Pick the right will for your situation
Trusted Hands supports three will types for couples:
- Mirror wills (£179) — two tied wills, each editable independently
- Mutual wills (£199) — two wills that legally bind each other
- Joint will (£189) — one document signed by both (offered for completeness; mirror wills usually better)
Not sure which? Try our Will Wizard — six questions, no email required, recommends the right type.