HOW TO CONDUCT A FAIR WORKPLACE INVESTIGATION

A practical guide for UK managers

A workplace investigation isn't about proving an allegation. It's about establishing what happened. This guide walks you through how to approach an investigation fairly, objectively and practically.

When something goes wrong at work, it's tempting to jump straight to the question:

"What action are we going to take?"

But before deciding on disciplinary action, you need to understand what actually happened. That's the purpose of a workplace investigation. A good investigation isn't about building a case against an employee. It's about gathering the facts, considering the evidence fairly and giving the business enough information to decide what, if anything, should happen next.

Get that stage wrong and everything that follows becomes more difficult.

WHAT IS A WORKPLACE INVESTIGATION?

An investigation is a fact-finding exercise. It may be needed following concerns about conduct, a grievance, bullying or harassment allegations, a workplace incident, policy breaches or other employee relations matters. The investigator's role isn't to decide what disciplinary sanction should be issued. Their job is to establish the facts. That means considering evidence that supports an allegation and evidence that doesn't.

The investigation should ultimately help the business answer:

What happened, what does the available evidence tell us, and is there a case that needs to be considered further?

1. Be clear about what you're investigating

Before booking meetings and writing questions, stop and define the issue. A vague investigation creates vague findings.

Instead of investigating:

"John's conduct."

you might be investigating:

"It is alleged that on 14 August, John used inappropriate and abusive language towards a colleague during an interaction on the shop floor."

That immediately gives the investigator something specific to establish.

Consider:

• What exactly is alleged to have happened?

• When and where did it allegedly happen?

• Who was involved?

• Which policies or expected standards may be relevant?

• Are there multiple allegations that should be considered separately?

For more complex investigations, setting clear terms of reference can help define the investigator's remit and prevent the investigation drifting into unrelated issues.

2. Make a plan before interviewing anyone

One of the easiest mistakes to make is immediately inviting people to investigation meetings.

First, work out what information you need.

Your investigation plan might identify:

• The allegations or issues being investigated

• The employee involved

• Potential witnesses

• CCTV

• Emails or messages

• System records

• Documents or paperwork

• Relevant policies and procedures

• Previous correspondence relevant to the incident

• Any evidence that could disappear or be overwritten

• The expected timeframe

The plan doesn't have to be complicated. Its purpose is to make sure you know what you're looking for and don't overlook obvious sources of evidence.

3. Choose the right investigator

Where possible, the investigator should not already be involved in the situation. They need to be capable of approaching the matter objectively and should have sufficient experience for the seriousness and complexity of the case. For example, an allegation involving potential gross misconduct, discrimination or serious bullying may require a more experienced investigator than a straightforward conduct concern. Where practicable in disciplinary cases, the person conducting the investigation should also be different from the person who would later chair any disciplinary hearing.

That creates clearer separation between:

Fact finding and Decision making.

4. Gather evidence - don't build a case

This distinction matters. You're not gathering evidence to prove the employee did something wrong. You're gathering evidence to understand whether they did. That means actively looking for information that could challenge the allegation as well as information that supports it.

If CCTV appears to support an allegation, look at the full relevant footage rather than only the ten seconds showing the incident. If one witness supports an allegation but another person was standing next to them, consider speaking to both. If an employee gives an explanation that can reasonably be checked, check it.

HR Unfiltered Take

An investigation isn't about proving the allegation happened. It's about establishing what happened. If you start an investigation looking for evidence to justify a decision you've already made, you're not really investigating.

5. Ask open questions

Good investigation meetings should allow people to give their account in their own words. Start broadly.

Instead of:

"Why did you shout at Sarah?"

ask:

"Talk me through what happened between you and Sarah."

Then explore the detail.

Useful investigation questions often include:

• What happened?

• What happened immediately before that?

• What happened next?

• Who else was present?

• What did you see or hear?

• What did you do?

• Why did you take that action?

• Is there anything that supports your account?

• Who else might have relevant information?

• Is there anything else you think I should consider?

Follow-up questions are where much of the useful information comes from.

If someone says:

"He became aggressive."

Don't simply write that down and move on.

Ask:

"What did he do that you considered aggressive?"

You need facts, not just descriptions.

6. Don't be afraid to challenge inconsistencies

Being impartial doesn't mean accepting everything you're told without question. If someone's account conflicts with another piece of evidence, explore it.

For example:

"You've said you left the building at approximately 6pm. The access record shows your pass being used at 6:37pm. Can you help me understand the difference?"

That's not an accusation. It's giving the person an opportunity to explain evidence that appears inconsistent with their account.

The same principle applies to witnesses. Your job is to test the information fairly, not simply collect statements.

7. Keep an open mind when new information appears

Investigations rarely follow a perfectly straight line. A meeting may identify another witness. An email may contradict an earlier account. CCTV may raise a completely different question. If relevant new information emerges, follow it.

That might mean:

• Speaking to another witness

• Reviewing additional documents

• Recalling someone for further questions

• Extending the investigation

• Reconsidering the scope

It's better to spend additional time establishing a relevant fact than rush to complete an investigation because you've already scheduled the next meeting. At the same time, investigations shouldn't drift indefinitely. They should be progressed without unreasonable delay while remaining sufficiently thorough and fair.

8. Consider the reliability of the evidence

Not all evidence carries the same weight.

Consider:

• Was the witness actually present?

• Could they clearly see or hear what happened?

• Was their account recorded shortly after the incident?

• Has their account changed?

• Is it supported by other evidence?

• Could there be a reason for bias?

• Does documentary or electronic evidence support the account?

• Are there reasonable alternative explanations?

Two witnesses saying the same thing doesn't automatically make something true. Equally, a lack of CCTV doesn't automatically mean something didn't happen. Evidence needs to be considered collectively and in context.

9. Document the investigation properly

Good notes matter. Six months later, someone who wasn't involved should be able to understand:

• What was investigated?

• What evidence was considered?

• What did people say?

• What was established?

• What remained disputed?

• How did the investigator reach their findings?

Your investigation report should be factual, structured and objective. Avoid unnecessary emotive language or presenting assumptions as facts. Where evidence conflicts, explain the conflict and how you assessed it. A good investigation report doesn't need to be 40 pages long. It needs to be clear.

10. Know where the investigation ends

This is another area where roles can become blurred. An investigator may conclude that there is sufficient evidence for the matter to proceed to a disciplinary hearing. That does not mean the employee is guilty or that disciplinary action has already been decided.

The disciplinary hearing is a separate stage at which the employee has the opportunity to respond to the allegations and evidence before a decision is made. Equally, an investigation may establish that there isn't sufficient evidence to justify further formal action.

That's a legitimate outcome.

HR Unfiltered Take

"No further action" doesn't mean the investigation failed. If you've investigated properly and the evidence doesn't support taking the matter further, the process has done exactly what it was supposed to do.

Common investigation mistakes

Some of the problems I see most often are surprisingly simple:

• Starting with a predetermined outcome

• Using vague allegations

• Asking leading questions

• Interviewing people without first gathering obvious evidence

• Failing to challenge inconsistencies

• Only looking for evidence that supports the allegation

• Treating opinion as fact

• Failing to follow up new information

• Poor or incomplete meeting notes

• Allowing the investigation to drag on unnecessarily

• Moving to a disciplinary hearing before the investigation is actually complete

• The investigator straying into deciding the disciplinary sanction

None of these necessarily requires a complicated solution. Usually, better planning and clearer thinking make the biggest difference.

The bottom line

A fair investigation isn't about producing the biggest evidence pack.

It's about being able to demonstrate that you approached the issue with an open mind, gathered the information that was reasonably necessary, gave people a fair opportunity to explain their account and considered the evidence objectively.

Before finishing an investigation, ask yourself:

• Do I understand what happened?

• Have I explored the reasonable alternative explanations?

• Have I considered evidence both for and against the allegation?

• Could another manager understand how I reached my findings from the documentation I've produced?

If the answer to those questions is yes, you're probably in a much stronger position to decide what happens next.

HR UNFILTERED

AUGUST 2026