A will isn't just a piece of paper saying who gets what. It's a legal document with strict requirements - and a surprising number of perfectly well-meaning wills are invalid the moment they're signed, sometimes only discovered years later when the family tries to apply for probate.
Here are the ten most common mistakes that invalidate or weaken a UK will, and how to avoid them.
1. The wrong people witness the signing
Under the Wills Act 1837, two adults must witness you signing the will. Both must be present at the same time, and each must then sign in your presence.
The single biggest mistake: a beneficiary (or their spouse/civil partner) acts as a witness. The will itself is still valid, but the gift to that beneficiary fails under section 15 of the Act. So if your daughter witnesses the will and you've left her your house, she gets nothing.
Fix: Choose two unrelated witnesses - neighbours, colleagues, friends - who aren't named in the will and aren't married or in a civil partnership with anyone in the will.
2. Witnesses sign at different times
The witnesses must be present together when you sign, and must each then sign in your presence. If one nips out for a coffee and signs separately, the will isn't validly executed.
This sounds pedantic but it's a real problem - especially with informal home signings and DIY kits. The signing ceremony is short. Block 10 minutes when everyone is in the same room.
3. Marriage revokes a previous will
This catches an enormous number of people. Getting married automatically revokes any will you had before, unless the will explicitly says it was made in expectation of that marriage.
The result: if you had a careful will, then got married and didn't update it, you're effectively intestate. See our intestacy guide for what happens then.
Fix: Re-do your will after any marriage, or if you're getting married, write the new will to say "this will is made in contemplation of my forthcoming marriage to [name]".
4. Divorce isn't quite a revocation
A common myth is that divorce revokes the will. It doesn't. After divorce, your ex-spouse is treated as having died before you for the purposes of the will - so any gifts to them lapse and any executor appointment to them is void. The rest of the will stands.
If your ex was the only beneficiary and only executor, you may end up with an unworkable will. Fix: review and ideally rewrite your will after any divorce.
5. Vague gifts that nobody can identify
"My silver to the children" - which silver? Whose children? "£5,000 to my friend Sarah" - which Sarah?
Vague gifts cause probate disputes. Use full legal names, state the relationship, and for items use specific descriptions ("my Patek Philippe wristwatch", "my 2018 Honda Civic registration AB18 XYZ"). For property, use the full address.
6. Forgetting the residual estate
A will should always include a residual clause - "I leave the rest of my estate to..." - that catches everything not specifically gifted.
Wills without a residual clause cause partial intestacy: anything not specifically named falls under intestacy rules and may go to people the testator never intended. This is more common with DIY kits than with guided services.
7. Not updating after children are born
If you wrote a will leaving everything to your spouse and then had children, the will may still work (everything still goes to the spouse, who then provides for the kids), but you may have missed appointing a guardian.
If both parents die without a guardian appointment in their will, the courts decide. See our guardians guide for what to think about.
8. The will isn't actually signed
Sounds absurd. It happens. People print a will, set it aside, and forget to sign it, or sign one copy and the family later finds an unsigned copy and assumes it's the real one. An unsigned will has no effect at all - the law treats it as if no will exists.
Fix: sign and witness immediately on printing, store the original somewhere known, and tell your executors where it is.
9. Storing the only copy somewhere it gets destroyed
A will that's lost or destroyed creates a presumption of revocation. If the original can't be found, the courts sometimes accept a copy with strong proof - but it's an expensive process, and not always successful.
Fix: keep the wet-ink original in a fireproof safe, with a solicitor, or with the Probate Service's wills storage facility (a one-off government fee). Tell your executors where it is.
10. Out-of-date executor or beneficiary details
The executor you appointed has emigrated. The charity you left £10,000 to has merged with another and changed its name. The cousin you left a quarter to has died.
These all have legal answers, but they cause delay and sometimes argument. Review your will every 3-5 years and after any significant life event.
When the testator lacked capacity
A will is only valid if the testator had mental capacity at the time of signing - meaning they understood:
- That they were making a will and what its effect would be.
- The extent of the property they were disposing of.
- The persons who might reasonably expect to benefit.
- That they were not affected by any disorder of mind influencing their decisions.
For elderly testators or those with a recent diagnosis (dementia, stroke, etc.), a contemporaneous medical opinion on capacity is sometimes recorded alongside the will to head off future challenges. A guided service flags this; some solicitors arrange it as standard.
When the testator was under "undue influence"
If a beneficiary pressured the testator into changing the will - shouting, isolating, threatening - the will (or the changed clauses) can be set aside. This is called undue influence. It's hard to prove, but contested cases do happen.
Trusted Hands records an explicit declaration that the will is being made of the testator's own free will - which is one of the things the complexity engine prompts before finalising.
> Ready to start your will? Trusted Hands turns these decisions into a 15-30 minute guided builder. Start free → — only pay when you download.
Frequently asked questions
Can I just amend my will by writing on it?
No. Any handwritten changes to a signed will are usually treated as void. Either re-execute (sign and witness) the new wording or use a properly executed codicil, or write a fresh will.
Does a will written abroad count in the UK?
It depends on where the property is and whether the foreign will complies with the formalities of either the country it was made in or where you were domiciled. For people with assets in multiple countries, two wills (one for each jurisdiction) are common. For complex estates, we recommend you seek assistance from a Trusted Hands Advisor or your own legal advice.
What happens if a will is found to be invalid after death?
The estate is treated as intestate (or, if there's an earlier valid will, that earlier will applies). See our intestacy guide for the consequences.
Can a will be challenged for any reason?
The main grounds are: lack of formal execution, lack of capacity, undue influence, fraud, lack of knowledge and approval (the testator didn't really understand what they were signing), and forgery. Beyond that, a person who was financially dependent on the deceased can apply for "reasonable provision" under the 1975 Act, but this isn't a challenge to the will itself.
Are witnessed wills via video link valid?
Temporary rules during the 2020-2024 period allowed video witnessing. From 31 January 2024 those rules expired and all wills must again be witnessed in person. Two witnesses, same room, same time.
The simplest way to avoid these mistakes is a guided will. Start yours with Trusted Hands - the system flags risky combinations as you go, and the witness guide takes you step-by-step through the signing.
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