The Personal Voice of Your Will

25 June, 2026 6 minutes reading time

Why confidential side documents are important to your estate plan

When you write a Will, you take a significant step to protect the people you love. But a Will is inherently a formal legal document. It has a specific role under the law: it sets out exactly who gets what. Because it must be legally precise, it rarely has room for personal explanations, practical advice, or the warm guidance your family will need during a difficult time.

That is where ‘side documents’ come in.

Side documents, also known as Letters of Wishes or Letters of Guidance, sit quietly alongside your Will. Crucially, they are not legally binding. They express your wishes rather than issue strict legal mandates. Even so, they are incredibly important. While they do not replace a Will, they do something priceless: they give you a personal voice when you are no longer there to speak for yourself.

So, how do these informal notes make your estate plan much more human, practical, and flexible?

1. Keeping Your Private Matters Private

Many people do not realise that once a Will goes through probate, it becomes a public document. Anyone can pay a small fee to look up your Will and read exactly how you distributed your estate.

Side letters, however, remain confidential in most cases. You write them directly to your executors or trustees, and they do not form part of the public probate record. If you need to share sensitive information, explain a personal choice, or give specific instructions to a trusted family member, a side letter keeps that conversation strictly behind closed doors.

English case law (Breakspear v Ackland) established that these letters are generally confidential, so beneficiaries have no automatic right to inspect them. However, confidentiality is not absolute. If appropriate, trustees may choose to share the letter to help manage the estate, and a court may order its disclosure in a legal dispute.

2. Changing Your Mind About Personal Belongings

If you want to leave small personal items (such as a watch, a piece of jewellery, or a family photo album) to specific people, naming them directly in your Will can cause headaches. If you sell the item, lose it, or buy something new, you must formally update your Will. That means hiring a solicitor, drafting an amendment (a codicil), and finding witnesses.

Instead, you can write a simple Memorandum of Wishes. As long as your Will contains a clause referencing this memorandum, you can update it whenever you like. You do not need witnesses, and you do not need to pay legal fees. You simply update the list, date it, and keep it with your Will.

Importantly, this flexibility applies only to personal belongings of lower financial value. Big assets like houses, shares, or large sums of money must always remain in the formal Will.

The Princess Diana Case Study

The estate of Princess Diana perfectly illustrates the dangers of drafting a side letter without professional oversight. In her Will, she left her estate to her sons. However, she also wrote an informal Letter of Wishes asking her executors to give one-quarter of her personal belongings (‘chattels’) to her 17 godchildren.

Because this list included exceptionally high-value assets (such as historic royal mementos and priceless jewellery) and because she used non-binding, polite language granting her executors broad ‘discretion’, her family was legally entitled to disregard it. Instead of receiving a share of the collection worth an estimated £100,000 each, the godchildren ultimately received just a single memento.

The Lesson: High-value assets should never be left to a side document; they belong in the formal Will itself. Furthermore, the precise legal phrasing of your side letters matters immensely to ensure your executors treat your wishes as instructions, not just optional suggestions.

3. Guiding the Care of Children and Trusts

If you have young children or a vulnerable relative, your Will might set up a trust to manage their inheritance. Choosing your trustees is the first step, but a Letter of Guidance tells them exactly how you want them to use that money.

Nobody knows your family dynamics better than you do. A side letter lets you pass on everyday wisdom that a formal Will cannot capture, such as:

• Your wishes for your children’s education, hobbies, or religious upbringing.

• How you want trustees to distribute funds for major milestones, such as a university fund or a house deposit.

• Specific instructions for vulnerable beneficiaries. For example, if a loved one relies on means-tested benefits, a carefully worded letter helps trustees manage funds safely without accidentally cutting off their state support.

While not legally binding, the UK Supreme Court (Pitt v Holt) confirmed that a person’s written wishes are a ‘material consideration’. This means your trustees are legally required to read and carefully weigh your guidance when managing your estate—they cannot simply ignore it. However, because they ultimately hold the final decision-making power, you must choose executors and trustees you trust completely.

4. Softening the Blow of Difficult Decisions

Inheritance disputes are unfortunately becoming more common. If you make a decision in your Will that might surprise or upset your family (such as leaving an unequal split between children or a gift to a charity instead of a relative), a sealed side letter can explain your reasoning.

Reading your explanation in your own words can defuse tension and help your family understand your choices. Furthermore, if someone decides to legally challenge your Will under the Inheritance Act, judges can review these confidential letters to understand your exact intentions. In this scenario, the letter provides essential protection for your final choices.

The Boundary Line

While side documents offer considerable flexibility, you must know where their authority ends. They are an effective way to update a list of personal heirlooms as your collection changes over the years.

However, they cannot address major life developments. If your personal circumstances change significantly (such as a child getting divorced, a relative passing away, or a remarriage that introduces step-grandchildren), you cannot simply amend a side letter.

Major family changes alter the legal structure of your family and your estate. When these milestones occur, a side letter is no longer sufficient; you will need to formally review and update your Will to ensure your choices remain secure. 

Our Advice

Getting the balance right is what matters. Side documents offer you incredible freedom, but they are a double-edged sword. They must support your Will, never contradict it. If a side letter inadvertently conflicts with a legal clause in your Will, it can cause confusion, delays, and stress for the very people you are trying to protect.

Writing these letters in plain, clear English is the best way to ensure your voice is heard exactly as you intend.

If you are reviewing your estate plan and want to ensure your Will and supporting documents work together seamlessly, contact us for a chat. We are here to help.

Please note that all views, comments or opinions expressed are for information only and do not constitute and should not be interpreted as being comprehensive or as giving legal advice. No one should seek to rely or act upon, or refrain from acting upon, the views, comments or opinions expressed herein without first obtaining specialist, professional or independent advice. While every effort has been made to ensure accuracy, Curtis Parkinson cannot be held liable for any errors, omissions or inaccuracies.

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