Internal investigations are rarely straightforward. A complaint about bullying, a suspected expenses fraud, or a regulatory breach can quickly become a legal minefield. One of the most important tools in your kit is legal privilege. Understanding when it applies, and how easily it can be lost, will help you run a fair process that protects your organisation's position. Get it wrong and your investigation notes could be disclosed to an employment tribunal or regulator. Get it right and you can have frank, protected conversations that get to the truth.

What legal advice privilege actually covers

Legal advice privilege protects confidential communications between a client and their lawyer, created for the dominant purpose of obtaining or giving legal advice. It does not require litigation to be underway. It can cover advice on how to handle a disciplinary process, a redundancy exercise, or an internal investigation. But it is narrower than many assume. The communication must be with a lawyer, and the advice must be legal – not merely commercial or operational. Asking your in-house legal team for a business view on a restructuring is unlikely to be privileged. Asking them how to comply with employment law during an investigation likely is.

Also, privilege does not usually extend to non-lawyers, such as HR consultants or external investigators, unless they are working under a lawyer's direction for the purpose of legal advice. So if you hire a non-lawyer to conduct interviews, those notes may not be protected.

Litigation privilege and internal investigations

Litigation privilege is separate and often more useful once a dispute is reasonably in contemplation. It protects confidential communications between the client or their lawyer and a third party, made for the dominant purpose of conducting litigation. This can include witness statements, expert reports, and correspondence with an external investigator. The key is that litigation must be reasonably in prospect – not just a vague worry. For example, if an employee has filed a grievance that looks likely to lead to an employment tribunal claim, litigation privilege may attach to documents created to defend that claim. But it does not cover documents created in the ordinary course of business, even if they later become relevant.

How privilege can be waived – and how to prevent it

Privilege is fragile. You can lose it in several ways:

• Sharing with the wrong people: Sending privileged advice to an external auditor, a non-executive director without a need to know, or a colleague outside the legal advice chain can waive privilege. Limit circulation strictly.
• Mixing legal and business advice: If a document contains both legal advice and commercial recommendations, a court may order disclosure of the whole document. Keep legal advice in separate documents.
• Putting advice in issue: If you rely on legal advice as part of your defence – for example, saying "we acted on legal advice" – you may waive privilege over that advice.
• Losing confidentiality: Leaving a draft report on a shared drive or discussing it in an open-plan office can destroy privilege. Treat privileged material like a secret.

Practical steps to protect privilege

Start early and be deliberate. Here is what works:

• Involve a lawyer from day one. Before you interview anyone or collect documents, speak to legal counsel. They can help you decide whether to structure the investigation under privilege.
• Document the purpose. Record that the investigation is for obtaining legal advice or in contemplation of litigation. This supports the dominant purpose test.
• Use a lawyer to lead interviews. Where privilege matters, have a lawyer conduct or attend interviews. Their notes are more likely to be protected.
• Mark and control documents. Label privileged material clearly and keep a log of who receives it. Use restricted folders.
• Separate legal from business advice. Ask for separate documents if you need both. A legal memo should not contain commercial strategy.

Early legal guidance makes the difference

Privilege is not a magic shield. It is a legal protection that requires deliberate action. Early legal guidance helps you avoid the common pitfalls and design an investigation that stands up to scrutiny. A lawyer can assess whether litigation is reasonably in contemplation, help you document decisions, and advise on tricky issues like employee interviews, data protection, and regulatory reporting. They can also advise when to waive privilege deliberately – for example, to share findings with a regulator – and how to do so in a controlled way.

Remember, the goal is not to hide the truth. It is to conduct a fair, thorough investigation while protecting your organisation's legal position. Privilege is a tool, not a cover-up. Used properly, it allows you to have candid conversations, gather evidence effectively, and make informed decisions. Without it, you may find yourself navigating a disciplinary or regulatory process with one hand tied behind your back. So before you send that first interview invite, pick up the phone to your legal team. A little planning now can save a lot of pain later.