Workplace Investigation Process UK: How Employers Should Decide When to Investigate

A workplace investigation should start with a question, not an allegation treated as fact.

When something happens at work, a complaint lands with a manager, an expense claim looks wrong, two employees give different versions of the same conversation, or somebody raises a concern about a senior colleague, there is often an understandable urge to move quickly. Someone wants an answer. Someone else wants the issue dealt with. The founder wants to know whether this is serious.

We think the first decision matters more than it gets credit for: does this situation actually need a workplace investigation, and if it does, what exactly are you investigating?

Acas says an investigation is the process of finding out all that an employer reasonably can about a possible disciplinary or grievance issue. Its purpose is to gather evidence from all sides, establish whether there is a case to answer, treat people fairly and help the employer decide what should happen next.

That sounds straightforward.

In practice, this is where a lot of cases either become manageable or become unnecessarily difficult.

A good workplace investigation process gives you enough reliable information to make the next decision fairly. It is not there to prove guilt, justify a conclusion the business has already reached, or necessarily end in a disciplinary hearing.

The conclusion might be that there is no case to answer, that an informal conversation would resolve the issue, or that the facts show the original concern was not the real problem at all.

We would rather discover that during an investigation than six weeks later at an appeal.

When should a UK employer carry out a workplace investigation?

A UK employer should investigate when there is a disciplinary or grievance issue that cannot fairly be understood or resolved without establishing more facts.

Acas says employers should investigate possible disciplinary and grievance issues by finding out all they reasonably can. A reasonable investigation is an important part of a fair procedure, and failing to investigate properly can make later decisions unfair.

That does not mean every disagreement at work needs a formal investigation.

We see situations where the word investigation gets used much earlier than it needs to.

A manager receives an abrupt email, two colleagues have argued, a deadline has been missed, or someone says a manager was rude.

There may be an issue there, but the first response can still be a sensible conversation.

The useful distinction is whether you already understand the relevant facts well enough to decide what happens next.

If you do, a formal investigation may add very little. If you do not, investigating becomes much more important.

What is the decision you actually need to make?

Before commissioning an investigation, write down the decision that the investigation is meant to help you make.

For example:

Is there enough evidence that company expenses were deliberately misused to justify formal disciplinary action?

That is much clearer than: Investigate James.

Or: What happened during the meeting on 4 August, and is there evidence that the behaviour described in the grievance took place?

That is clearer than: Investigate the bullying complaint.

The difference matters because an investigation without a defined question tends to expand. One witness mentions another issue, that leads to another document, another employee recalls something from six months ago, and the investigator starts looking at the general working relationship.

Three weeks later, everyone has forgotten what the original concern was.

Clear scope is not bureaucracy. It is how you stop an investigation becoming an open-ended search for problems.

Can a workplace issue be resolved without a formal investigation?

Yes. Acas makes clear that an employer can consider at any stage whether an issue could be resolved informally instead, or whether the formal procedure needs to continue.

We think this is particularly relevant for growing businesses.

Smaller organisations often have closer working relationships than large employers. That can make problems feel more personal, but it can also make early resolution easier.

Imagine an employee complains that their manager repeatedly excludes them from meetings.

You might initially think: grievance investigation.

But a first conversation may establish that the meetings relate to a project the employee no longer works on and nobody explained the change.

That does not mean every concern can be talked away. It means the response should match the problem.

If there are disputed allegations, serious misconduct, possible discrimination, bullying, harassment, fraud, safeguarding concerns or consequences that could significantly affect someone's career, a proper investigation is much more likely to be needed.

Where the issue is straightforward and accepted by everyone involved, a lighter approach may be enough.

The question we keep coming back to is: What do we still need to know before we can make a fair decision?

If the answer is "nothing", you may not need a lengthy investigation.

What should a workplace investigation establish?

A workplace investigation should establish the relevant facts, including evidence that supports the concern and evidence that does not.

Acas specifically says an investigator should be fair and objective, obtain as much information as is reasonable, and avoid trying to prove guilt. The investigator should consider evidence from both sides.

That last point is important.

There is a very different mindset between: We think this happened. Find the evidence. And: This has been alleged. Find out what happened.

Only the second is an investigation.

Once an investigator becomes personally invested in proving the allegation, perfectly ordinary choices start to change. A supporting witness gets interviewed twice. A contradictory witness gets treated as unreliable. An email that supports the employee is described as lacking context. An email against the employee is described as compelling.

Nobody necessarily believes they are being unfair. That is why the structure matters.

Case study: Shrestha v Genesis Housing Association Ltd

Shrestha v Genesis Housing Association Ltd [2015] EWCA Civ 94 is useful because it shows what a reasonable investigation does, and does not, require.

Mr Shrestha worked as a floating support worker and claimed mileage expenses for travelling to clients. An audit found substantial differences between mileage claimed and expected journey distances. He gave several explanations, including parking problems, roadworks, road closures and one-way systems. He was eventually dismissed for gross misconduct relating to fraudulent mileage claims.

His argument was that the employer should have investigated each explanation individually.

The Court of Appeal disagreed.

The court held that the investigation should be considered as a whole when deciding whether it was reasonable. Employers must consider explanations put forward by an employee, but they do not automatically have to investigate every suggested line of defence to exhaustion. What is necessary depends on the circumstances.

We think that is a useful principle for SMEs.

A reasonable investigation needs to be thorough enough. It does not need to become limitless.

If five witnesses give the same undisputed account, interviewing another ten people who saw nothing may add very little. If an employee raises a specific explanation that could materially change the case, ignoring it would be much harder to justify.

Reasonableness sits between those two extremes.

How thorough does a workplace investigation need to be?

The investigation should be proportionate to the seriousness, complexity and potential consequences of the issue.

Acas recognises that some investigations can be completed quickly while others may take several weeks, depending on the facts and the number of people involved. The process should move as quickly as reasonably possible, but not at the expense of fairness or thoroughness.

There is no sensible rule saying: every workplace investigation takes 10 working days.

The allegation decides the work.

Repeated lateness might be established through attendance records, the employee's explanation and previous management conversations.

An allegation of sexual harassment involving conflicting witness accounts may require interviews, messages, event records and careful consideration of what happened before and after the alleged incident.

A serious allegation involving somebody's professional reputation may justify an especially careful investigation.

Case study: Tykocki v Royal Bournemouth and Christchurch Hospitals NHS Foundation Trust

Tykocki v Royal Bournemouth and Christchurch Hospitals NHS Foundation Trust, UKEAT/0081/16/JOJ involved a healthcare assistant accused by a patient of serious mistreatment.

The allegations included that the employee had covered the patient's mouth with her hand and told her to be quiet. She denied the accusations. The matter had obvious consequences for both her employment and professional reputation.

One problem considered during the case was the way additional evidence from the patient had been handled. Further allegations emerged, but the employee was not given a proper opportunity to respond to all of that material before the employer made its decision.

The Employment Appeal Tribunal stressed the need to take particular care where serious allegations could have major consequences for an employee.

There is a useful commercial lesson here that goes beyond healthcare.

The more serious the allegation and the greater the potential consequence, the less comfortable you should be with shortcuts.

If somebody may lose their job, reputation or ability to continue in their profession, the investigation needs to reflect that seriousness.

Who should conduct a workplace investigation in the UK?

The investigator should normally be someone who is not involved in the issue and who can approach the evidence objectively.

Acas recommends appointing somebody without a conflict of interest, such as another manager or a member of HR. Where possible, the investigator should have relevant training and understand the organisation's investigation procedure. More serious or complex issues may justify using somebody more experienced or senior.

That sounds easier in a 2,000-person business than in a 45-person company.

We know.

In founder-led businesses, senior people tend to know what is happening. The founder may have received the complaint. The operations director may already have spoken to both parties. The most experienced manager may supervise the person being investigated.

That does not automatically make a fair investigation impossible. It does mean you need to think deliberately about independence.

Acas says that where complete separation is not possible, employers should make the process as impartial as they reasonably can.

That might be another internal manager, a member of HR, or in some cases an external investigator where a cleaner separation is needed.

When does an external investigator make sense?

We would usually think seriously about independence where:

• the allegation involves a founder, board member or senior leader

• internal HR has already advised extensively on the situation

• several members of senior management are witnesses

• the complaint involves discrimination, bullying or harassment

• the investigation could lead to dismissal or significant reputational consequences

• there is nobody internally with the time or experience to run the process properly

• trust in the internal process has already broken down

An external investigator should not be brought in merely to make an ordinary management issue look more serious. But there are cases where independence is worth paying for.

The point is not that an external investigator is automatically better. The point is that the person investigating needs enough distance to follow the evidence wherever it goes.

Should the investigator also chair the disciplinary hearing?

Where possible, no.

For a disciplinary case, Acas recommends using different people for the investigation, disciplinary hearing and appeal where the organisation has enough people to do that.

This matters because the jobs are different.

The investigator asks: What happened, and is there a case to answer?

The disciplinary chair asks: Having heard the case and the employee's response, what finding and outcome are appropriate?

The appeal manager asks: Was the original decision fair and reasonable, and does anything need reconsidering?

Combining all three roles makes it harder to demonstrate fresh judgement at each stage.

In a very small organisation, complete separation may not be possible. If that is your situation, document why, and create as much independence as you reasonably can.

Do not pretend a five-person company can operate like a government department. But equally, do not let convenience become the only factor.

What should terms of reference for a workplace investigation include?

Terms of reference should define what the investigator is being asked to investigate, the scope of their role, how findings will be presented and whether they are expected to make recommendations.

Acas specifically recommends clear terms of reference because they help establish the investigator's remit and keep the investigation focused.

For most SME investigations, we would want the terms of reference to answer four questions:

• What is being investigated? State the allegation or issue as neutrally and specifically as possible.

• What is outside scope? This is often just as important.

• What is the investigator being asked to conclude? Usually whether particular facts are established and whether there appears to be a case to answer.

• Are recommendations required? Some employers want the investigator to recommend next steps. Others want a factual report only.

Set that expectation before the investigation begins. Otherwise, the investigator can end up deciding the sanction without anyone having asked them to.

How should a UK employer plan a workplace investigation?

Acas recommends creating an investigation plan covering the issue, investigator, witnesses, evidence sources, relevant deadlines, timescales, policies and confidentiality.

We would add one thing: identify what might disappear.

CCTV may be overwritten. Slack messages may be deleted. A contractor may finish their assignment. A witness may leave for three weeks. Someone may resign.

Evidence does not always sit patiently waiting for the investigation timetable.

The first 24 to 48 hours can therefore matter.

That does not mean interviewing everybody immediately. It means preserving what could otherwise be lost.

What evidence should you collect in a workplace investigation?

Collect evidence that is relevant to the allegation and reasonably available.

Acas gives examples including emails, documents, receipts, computer records, phone records, CCTV, attendance data and vehicle tracking information. Employers must also consider privacy, data protection and whether their monitoring practices allow the information to be used in this way.

The important word is relevant.

More evidence does not automatically mean a better investigation.

A folder containing 1,500 emails is not evidence analysis.

Someone still has to determine:

• what the material shows

• when it was created

• whether it is reliable

• whether important context is missing

• whether it supports or contradicts other evidence

We often find the chronology is the best place to start.

What happened first? What happened next? Who knew what at each stage?

A good chronology can expose gaps surprisingly quickly.

When should employees and witnesses be interviewed?

In potential disciplinary cases, Acas recommends considering interviewing the employee under investigation at an early stage. That can help establish which facts are actually disputed and focus the remaining work.

This is a good example of why investigations should not be designed backwards.

Some investigators collect every document and interview every witness before speaking to the person accused.

Then the employee says: I agree I sent the email. My account was hacked that morning and IT already investigated it.

Suddenly half the investigation was unnecessary.

Early engagement can narrow the issue.

Witness interviews should then focus on what that person actually knows.

Not: What have you heard about what happened?

But: What did you personally see, hear or do?

That distinction prevents rumour becoming evidence.

Acas recommends neutral, non-confrontational questioning and giving witnesses an opportunity to review and confirm the accuracy of their statement.

Should a workplace investigation be confidential?

Usually, yes.

Acas recommends keeping investigations confidential where possible to reduce harm, protect working relationships, reduce the possibility of witnesses coordinating accounts and support data protection obligations.

Confidential does not mean secret.

The person being investigated needs enough information to understand the concern. Witnesses may need to know why they are being interviewed. Representatives may need relevant information.

The practical rule is: share what people reasonably need for the process, not everything everyone wants to know.

We would also avoid promises of absolute anonymity to witnesses unless there is a very good reason.

If evidence is going to influence a disciplinary decision, the employee will usually need a fair opportunity to understand and respond to it.

Should an employee be suspended during a workplace investigation?

Suspension should be considered carefully, not treated as the default response to a serious allegation.

Acas says suspension is only necessary in some situations and employers should consider alternatives and the effect suspension can have on the person's wellbeing.

We think the question should be: What risk are we trying to control?

Possibilities might include:

• interference with witnesses

• destruction or alteration of evidence

• safeguarding concerns

• risk to clients or colleagues

• continuation of the alleged conduct

Once you identify the risk, consider whether something less disruptive would manage it.

Temporary reporting-line changes. Restricted system access. Home working. Different duties. Adjusted shifts.

Suspension may still be appropriate. But it should follow a decision, not replace one.

In UK employment practice, suspension during an investigation will usually be on full pay unless the employee's contract clearly provides otherwise.

What should a workplace investigation report include?

A workplace investigation report should explain what was investigated, the evidence considered, which facts were established or not established, any relevant mitigating circumstances and the investigator's conclusions.

Acas says the final report should be objective, factual, concise and include the evidence collected. The report should reflect the investigator's own conclusions.

A practical workplace investigation report template for a UK employer could use this structure:

• Background and terms of reference. What issue triggered the investigation and what was the agreed scope?

• Method. Who was interviewed? What documents or other evidence were reviewed? Were there any limitations?

• Allegations or questions considered. Deal with each issue separately.

• Evidence. Summarise relevant evidence supporting and contradicting each allegation.

• Findings of fact. State clearly which facts are established, not established or remain uncertain.

• Conclusion. Explain whether the evidence indicates there is a case to answer or whether another next step is appropriate.

• Appendices. Include relevant statements and supporting evidence.

The report does not need dramatic language. In fact, the calmer it is, the better.

A good report should allow somebody who was not involved in the investigation to understand how the investigator moved from evidence to conclusion.

Case study: Ramphal v Department for Transport

Ramphal v Department for Transport, UKEAT/0352/14/DA is a useful case when thinking about who actually owns the investigation report.

Mr Ramphal faced allegations concerning his use of hire cars and a company credit card. During the disciplinary process, the investigating manager received substantial HR input. The Employment Appeal Tribunal was concerned that some of that input went beyond advice on procedure and law and moved into questions of culpability.

The principle is useful even outside disciplinary cases.

HR can advise an investigator. A lawyer can advise on legal risk. A senior manager can ask whether something has been explained clearly.

But the investigator's findings should remain the investigator's findings.

We would be very uncomfortable with an investigation report that changes from: We found no evidence of dishonesty. To: We found serious concerns regarding integrity. Because somebody senior preferred the second version.

Advice is legitimate. Replacing the investigator's judgement is something else.

What happens when the investigation is finished?

The investigation should not normally determine the disciplinary outcome. Its purpose is to establish what the evidence supports and help the employer decide the appropriate next step.

Acas says the investigator's recommendations, where the terms of reference allow recommendations, could include formal action, informal action or no further action.

That third option matters.

We have seen investigations where everyone assumed from day one that there would be a disciplinary hearing.

Then the evidence did not support the allegation.

That is not a failed investigation. That is the investigation working.

Equally, an investigation may identify a genuine problem that is better resolved through mediation, coaching, a management conversation or changes to a policy.

The process exists to help the business make a better decision. Not to produce a disciplinary outcome.

Disciplinary investigation checklist for a UK employer

Before starting or approving a workplace investigation, we would check the following:

• Define the concern. Can you describe the issue neutrally in one or two sentences?

• Decide whether investigation is necessary. Could an informal conversation reasonably resolve it?

• Choose the right investigator. Are they sufficiently independent, experienced and available?

• Set terms of reference. What is inside and outside scope?

• Preserve evidence. Is there CCTV, digital information or witness availability that could be lost?

• Plan interviews. Who has first-hand relevant information?

• Tell the employee. Explain what is happening unless there is a genuine evidence or witness risk in doing so immediately.

• Consider confidentiality. Who genuinely needs information about the case?

• Consider suspension separately. What risk would it manage and are there alternatives?

• Test both sides of the evidence. What supports the allegation and what contradicts it?

• Record limitations. What could not be established, obtained or verified?

• Write an objective report. Separate evidence, findings and recommendations.

• Keep the investigator's judgement independent. Advice can inform the report but should not replace the investigator's conclusions.

• Decide the next step afresh. Formal action, informal action or no further action are all legitimate outcomes.

If the investigation cannot pass those checks, we would usually fix the process before moving into a disciplinary hearing.

How JourneyHR can help

We are regularly brought into workplace investigations when the business needs additional capacity, independence or senior HR judgement.

Sometimes the allegation involves a founder or senior leader and nobody internally can investigate without a conflict.

Sometimes the internal People team is perfectly capable but already too involved in the events.

Sometimes a manager has started an investigation and realises halfway through that the issue is much more complex than expected.

And sometimes the useful call is the one before any investigation begins, because the real question is whether formal investigation is needed at all.

JourneyHR's Employee Relations team works with businesses on grievances, disciplinary matters, bullying and harassment investigations, hearings and appeals. We can work alongside your internal team or act as the external investigator where an independent process makes more sense.

Our role is not to make every employee issue more formal. It is to help you establish what happened, treat the people involved properly and reach a decision you can explain.

If you have a workplace issue in front of you now and are deciding whether to investigate, we are happy to talk through the facts and tell you what we think the sensible next step is.

Get in touch: JourneyHR contact page

Final thought

The best workplace investigations tend to start smaller than people expect.

The best investigations start with a clear question, a sensible investigator and a defined scope. Evidence comes from both directions, and the investigator follows wherever the facts lead.

The investigation does not need to prove somebody right. It needs to leave the business in a better position to make the next decision fairly.

That is what we would get right first.

This article is for general guidance only and should not be treated as legal advice.

FAQs

How do you conduct a workplace investigation in the UK?

Start by defining the issue and deciding whether formal investigation is genuinely necessary. If it is, appoint an impartial investigator, set clear terms of reference, identify evidence and relevant witnesses, speak to the employee and witnesses fairly, and consider evidence both for and against the allegation. The investigator should then produce an objective report setting out established and unestablished facts and any agreed recommendations.

Who should conduct a workplace investigation in the UK?

Ideally, the investigator should be someone who has not been involved in the issue and has no conflict of interest. Acas suggests another manager or HR, with more experienced or senior investigators used for serious or complex matters. An external investigator can be appropriate where internal independence is difficult, particularly for allegations involving senior leaders, harassment, discrimination or other sensitive matters.

Does an employer have to investigate every complaint formally?

No. Employers should consider whether an issue can reasonably be resolved informally before or during a formal process. The important question is whether the employer has enough reliable information to make a fair decision. Where facts are disputed, allegations are serious or the potential consequences for the employee are significant, a more formal investigation will usually be appropriate.

What should be included in a workplace investigation report?

A workplace investigation report should normally include the investigation's background and scope, the evidence considered, relevant witness information, findings on each issue, facts that were established or not established, any important mitigating circumstances and the investigator's conclusions. Acas recommends that reports are objective, factual, concise and reflect the investigator's own judgement rather than somebody else's preferred outcome.

How long should a workplace investigation take in the UK?

There is no single legal timeframe for every investigation. Acas says employers should complete investigations as quickly as reasonably possible while still being thorough and fair. A simple issue may take a day to investigate, while a complex matter involving several witnesses or serious allegations can take weeks. If the timetable changes, the employer should explain delays to the people involved.