The five requirements that make a will legally valid
Section 9 of the Wills Act 1837 sets out the law in plain terms. Meet these five requirements and your will is legally binding:
- The will is in writing — handwritten, typed, or printed.
- The testator (the person making the will) is aged 18 or over and has testamentary capacity.
- The will is signed by the testator, or signed by someone else in their presence and at their direction.
- The signature is made or acknowledged in the presence of two witnesses present at the same time.
- Each witness then signs the will in the presence of the testator.
That is the whole legal test. There is no requirement that a solicitor draft the will, no requirement that the will be filed anywhere, and no requirement that it follow a particular template. The Probate Registry, when granting probate, checks the document against these five requirements — nothing more.
Common ways wills fail the validity test
Wills that fail in probate almost always fail on execution, not drafting. The classic failures:
- Wrong number of witnesses. One witness is not enough; you need two.
- Witnesses not present at the same time. Both must watch you sign — you cannot sign first, then have witness 1 add their signature, then witness 2.
- A witness is also a beneficiary. If a beneficiary or their spouse witnesses the will, the gift to that beneficiary is void (though the rest of the will stands).
- Testator lacks capacity. If the testator did not understand what a will is, what their assets are, and who they are providing for, the will is void.
- Undue influence. A will signed under pressure from a beneficiary can be set aside.
- The signature is not on the document. Initialling pages is not signing — the testator's full signature must appear once.
Witnessing — the most important rule to get right
Both witnesses must be:
- Aged 18 or over
- Of sound mind
- Present in the room when you sign — physical presence, both at the same time
- Not a beneficiary of the will
- Not married to or in a civil partnership with a beneficiary
Good witness choices: a neighbour, a colleague, a friend who is not in the will. Bad choices: your spouse if they're benefiting, your adult children if they inherit anything, your business partner if they get a specific bequest.
Capacity — what the law actually requires
Testamentary capacity, settled by case law (notably Banks v Goodfellow), means the testator must:
- Understand what a will is and what its effect will be
- Understand the extent of their assets
- Understand and consider any moral claims they should give effect to (e.g., adult children, dependants)
- Not be suffering from any disorder of mind that perverts their judgement
For most healthy adults this is straightforward and assumed. Where there is doubt — early dementia, recent serious illness — a doctor's letter at the time of signing is good practice and often resolves later disputes.
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Start Mirror WillsHow we compare on price
| Provider | Single Will | Mirror Wills | Format |
|---|---|---|---|
| ClearLegacy | £69 | £99 | Online · estate-planner reviewed · 24-hour turnaround |
| Farewill | £100 | £165 | Online · review-by-phone |
| Co-op Legal Services | £150+ | £245+ | Phone or online |
| High-street solicitor | £150–£400 | £250–£600 | Face-to-face appointments |
| DIY kit (WHSmith etc.) | £20–£40 | £40–£80 | Paper · no review |
Prices are typical published rates at time of writing (May 2026). Sources: provider websites; Law Society for solicitor ranges.
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