Workplace investigations: a practical guide

A practical guide to workplace investigations for UK employers, covering when to investigate, how the process works, who should lead it, and when external investigation support may help.

A workplace investigation is one of the most important processes an employer may need to carry out when concerns are raised at work.

A grievance lands. A bullying allegation is raised. A manager reports misconduct. A senior employee is accused of inappropriate behaviour. At that point, the organisation needs to respond carefully, fairly and without making assumptions.

A poorly handled workplace investigation can create real problems. It can expose the organisation to tribunal risk, damage trust, unsettle teams and lead to unfair outcomes for everyone involved. It can also make a difficult situation worse, which is rarely anyone’s objective.

This guide explains what a workplace investigation is, when an employer should investigate, how the investigation process works, and when it may be sensible to bring in independent support.

At Cornerstone, we have conducted many investigations across grievances, disciplinaries, bullying and harassment concerns, senior-level complaints and complex workplace conflict. One thing we always keep in mind is that, for the employee involved, this may be the first time they have ever been part of a formal process. That matters. The process must be robust, but it should also be human.

Our approach is built around the TCM FRESH investigation model: Fair, Rigorous, Equitable, Sensitive and Honest. In practice, that means a clear, structured and proportionate process that treats people fairly while keeping a firm focus on the evidence.

What is a workplace investigation?

A workplace investigation is a fact-finding process used to understand what has happened before an employer makes a decision.

It is not a disciplinary hearing or a grievance outcome. The investigator’s role is to establish the facts, not to decide the final sanction or outcome.

The investigator gathers relevant evidence, speaks to the people involved, reviews documents or records where needed, and produces findings based on the evidence available. What happens next should usually be decided by someone else. 

A typical workplace investigation may involve:

• the investigator, who gathers evidence and prepares the report;
• the complainant, who has raised the concern or grievance;
• the respondent, who is the person the allegation or concern relates to;
• witnesses, who may have relevant information;
• HR or an external adviser, who may support the process and ensure it is fair.

In a grievance investigation, one of the most important early questions is: what outcome is the complainant hoping for?

That does not mean promising they will get that outcome. It means understanding whether they want an apology, a change in working arrangements, action against another employee, mediation, clearer communication, or simply to be heard. Without that understanding, an employer can run a technically competent process and still miss the real issue.

When should an employer carry out a workplace investigation?

Not every workplace issue needs a formal investigation.

Some concerns can be resolved through an informal conversation, a facilitated conversation or mediation, protected conversation, management intervention or clarification of expectations. A full investigation is not always the right tool. Sometimes it is the workplace equivalent of using a sledgehammer to crack a nut.

However, a formal workplace investigation is usually needed where there are disputed facts, serious allegations, potential disciplinary consequences, or where the organisation needs a clear evidence base before deciding what to do next.

Common triggers include:

• formal grievances;
• bullying or harassment allegations;
• discrimination concerns;
• whistleblowing disclosures;
• misconduct allegations;
• serious breakdowns in working relationships;
• safeguarding concerns;
• complaints involving senior employees;
• repeated issues where informal action has not worked.

The key question is whether the employer can make a fair and reasonable decision without further fact-finding. If not, an investigation is likely to be needed.

It is also worth pausing before launching straight into a formal process. If the issue is mainly relationship-based, rather than conduct-based, it may be better to consider when workplace mediation may be more appropriate than a formal investigation or to look at understanding the full range of conflict resolution options.

The wrong process can make conflict more entrenched. The right process can help people move forward, even when the facts are uncomfortable.

What should an employer do before starting a workplace investigation?

The quality of an investigation is often decided before the first interview takes place.

Before starting, you should be clear about the purpose of the investigation. What exactly needs to be investigated? What questions need answering? What policies apply? Who is the right person to investigate? What evidence may need to be preserved? Are there any conflicts of interest?

This is where clear terms of reference matter. They should set out the scope of the investigation, the allegations or issues being considered, the relevant policies, the expected timescales, and what the investigator is being asked to produce.

A vague investigation creates vague findings. Vague findings rarely help anyone.

Before starting, you should also consider whether suspension is necessary. Suspension should not be automatic. It may be justified where there is a serious risk to the investigation, health and safety, evidence, witnesses, clients, service users or working relationships. However, it should be a neutral act, kept under review and handled carefully. Poorly managed suspension can feel punitive and can undermine trust before the investigation has even begun.

You should also think about confidentiality from day one. People involved in the process should understand that confidentiality is expected, but they should not be promised complete secrecy. Evidence may need to be shared as part of the process, particularly where fairness requires the respondent to understand the case against them.

If the matter is sensitive, senior, complex or carries legal risk, it is sensible to speak to an HR consultant before starting your investigation.

How to conduct a workplace investigation, step by step

A good workplace investigation is structured, but not rigid. The investigator needs a clear plan, while remaining open to new evidence as it emerges.

The process will vary depending on the issue, but most investigations follow these broad stages.

1. Confirm the terms of reference

Start by confirming what is being investigated. This may be a single allegation, a series of incidents, a formal grievance, or a broader concern about conduct or culture.

The investigator should understand their role. Their task is to establish the facts, not to decide the sanction or outcome.

2. Review the relevant documents

This may include policies, contracts, emails, messages, rotas, CCTV, HR records, previous meeting notes, absence records, performance records, audit trails or client correspondence.

Digital evidence should be handled carefully. Employers should avoid broad fishing exercises and should ensure any review of electronic material is lawful, proportionate and consistent with privacy notices and IT policies.

3. Identify who needs to be interviewed

The investigator should usually speak to the complainant first, then the respondent, then relevant witnesses. That order may change depending on the circumstances.

The aim is not to interview everyone who has an opinion. It is to interview people who may have relevant evidence.

4. Plan the investigation questions

Good questioning is central to a fair investigation.

Start with open questions that allow the person to give their account in their own words. Then use more focused questions to clarify dates, times, locations, exact words used, witnesses, documents and impact.

For example:

“Can you talk me through what happened?”

“What did you see or hear?”

“When did this take place?”

“Who else was present?”

“What happened immediately afterwards?”

“Is there any document, message or record that may support your account?”

“Is there anything else you think I need to know?”

Avoid loaded questions, assumptions and cross-examination. This is not a courtroom drama. No one needs a “gotcha” moment. They need a fair opportunity to explain.

5. Conduct the interviews fairly

At the start of each meeting, explain the purpose of the investigation, the investigator’s role, who is present, how notes will be taken, how information may be used, and the importance of confidentiality.

It is good practice to allow someone to be accompanied where reasonable, even where there is no strict legal right at an investigatory meeting. This can be particularly important where the person is anxious, vulnerable, disabled, or facing serious allegations.

For many people, being invited to an investigation meeting is intimidating. A calm, clear opening can make a significant difference to the quality of information gathered.

6. Take accurate notes

Notes should be clear, balanced and contemporaneous. They should record what was said, not what the investigator wished had been said.

Interviewees should usually be given the opportunity to review and confirm their notes or statements. If they disagree with the notes, this should be recorded.

7. Test the evidence

The investigator should look for evidence that supports and challenges each allegation. They should not simply gather material that confirms an early view.

Where accounts conflict, the investigator should consider consistency, detail, timing, documents, plausibility and whether there is supporting or contradictory evidence.

The standard is usually the balance of probabilities: what is more likely than not to have happened?

8. Prepare the investigation report

The report should be clear, factual and structured. It should usually include:

• the background;
• the terms of reference;
• the process followed;
• the evidence reviewed;
• the people interviewed;
• the findings against each allegation or issue;
• the rationale for those findings;
• any recommendations within the investigator’s remit;
• appendices containing relevant documents and statements.

The report should not overreach. If the investigator has been asked to recommend next steps, that may include no further action, informal resolution, mediation, training, policy review, or referral to a disciplinary hearing. It should not normally recommend dismissal or a specific sanction. That is for the decision-maker.

Who should carry out a workplace investigation?

The investigator should be fair, impartial, available, capable and sufficiently senior or credible to carry out the role.

An internal investigator may be appropriate where they have no involvement in the matter, no conflict of interest, enough time to complete the process, and the skills to handle the investigation properly.

An external investigator may be better where:

• the allegations involve senior employees;
• the organisation is small and independence is hard to demonstrate;
• there are cross-departmental issues;
• previous internal attempts have failed;
• there is a risk of perceived bias;
• the matter involves bullying, harassment, discrimination or whistleblowing;
• the case carries significant legal, reputational or safeguarding risk;
• internal managers do not have the time, confidence or experience to investigate properly.

Independence is not just about being fair. It is also about being seen to be fair.

That matters because an investigation that is not trusted by those involved can create further grievances, appeals, sickness absence and legal risk.

You can find out how Cornerstone supports employers with independent workplace investigations where internal investigation is not the safest or most credible option.

What rights does an employee have during a workplace investigation?

Employees involved in a workplace investigation should be treated fairly, respectfully and without prejudgment.

They should usually be told that an investigation is taking place and why. The level of detail will depend on their role in the process and the nature of the allegations, but the respondent should have enough information to respond properly.

Employees should also be told what is expected of them, including confidentiality, attendance at meetings, providing relevant evidence and cooperating with reasonable instructions.

There is not usually a statutory right to be accompanied at a purely investigatory meeting, unless the employer’s policy provides for it or the meeting effectively becomes part of the formal disciplinary or grievance hearing. However, allowing accompaniment is often sensible and supportive, particularly in sensitive cases.

Employees should not be victimised or subjected to detriment for raising a genuine concern, grievance, discrimination complaint or whistleblowing disclosure. Equally, respondents should not be treated as guilty before the facts have been established.

The employer should keep the process proportionate, avoid unreasonable delay, make reasonable adjustments where needed, and keep parties updated. Silence during an investigation rarely helps. It usually creates worry, speculation and mistrust.

What happens after a workplace investigation?

Once the investigation is complete, the report should usually be provided to the appropriate decision-maker.

The decision-maker will then consider the findings and decide what happens next. Depending on the case, the options may include:

• no further action;
• informal resolution;
• a grievance outcome;
• mediation or facilitated conversation;
• training or coaching;
• policy or process changes;
• management action;
• referral to a disciplinary hearing;
• further investigation if important gaps remain.

The investigation report should be handled carefully. It may contain sensitive personal data and should be shared only with those who genuinely need to see it. Employers should also consider data protection obligations, retention periods and whether redactions are needed before sharing documents.

If the investigation forms part of a disciplinary or grievance process, the employee should be told the outcome of that process and usually given the right of appeal where a formal decision is made.

It is also important to think about what happens after the formal process ends. Relationships may still be strained. A complainant may feel disappointed. A respondent may feel embarrassed or angry. Witnesses may feel exposed. Teams may be unsettled.

This is where the organisation needs to look at the full range of conflict resolution and formal procedures available, not just the investigation report.

An investigation may close the facts. It does not automatically repair the workplace.

Common mistakes employers make during a workplace investigation

The most common investigation mistakes are usually avoidable.

One of the biggest is deciding the outcome before the evidence has been gathered. Once that happens, the investigation becomes a staged exercise rather than a fair process. Tribunals are very good at spotting that.

Another common mistake is failing to define the scope. If the investigator does not know what they are investigating, the process can drift, expand unnecessarily or miss the key point entirely.

Employers also get into difficulty when they:

• suspend automatically without considering alternatives;
• use the same person to investigate and decide a disciplinary outcome where separation is practicable;
• fail to preserve confidentiality;
• leave employees without updates for weeks;
• do not keep proper records;
• ask leading or aggressive questions;
• ignore evidence that does not fit the preferred narrative;
• fail to make reasonable adjustments;
• make findings based on assumptions rather than evidence;
• allow senior leaders to influence the investigator’s conclusions;
• make recommendations outside the investigator’s remit;
• forget to plan for reintegration after the outcome.

A good investigation is not about making the employer’s preferred outcome look tidy. It is about getting as close as reasonably possible to the facts, using a process that is fair, proportionate and capable of withstanding scrutiny.

When should you use an external workplace investigator?

External support can be particularly helpful where independence, experience or credibility is essential.

That may be because the allegations are serious, the parties are senior, internal relationships are too close, or the organisation does not have someone with the right skills and capacity to investigate well.

This can be especially relevant for SMEs, charities and owner-managed businesses, where it may be harder to show clear separation between the people involved and the person leading the process.

An external workplace investigation consultant can help by:

• agreeing clear terms of reference;
• planning the investigation;
• conducting interviews;
• reviewing relevant evidence;
• preparing a structured investigation report;
• identifying whether there is a case to answer;
• making appropriate recommendations within remit;
• supporting a fair and defensible process.

At Cornerstone, we bring structure, independence and calm to difficult situations. We understand that investigations are not just technical processes, but experiences that can be challenging for everyone involved.

If you are unsure whether you need an internal or external investigation, or if a matter has already started to escalate, you can get in touch to discuss your investigation requirements or find out about Cornerstone’s independent investigation service.

A workplace investigation will not always be comfortable. But handled properly, it can give everyone involved something important: a fair process, a clearer understanding of the facts, and a better basis for deciding what happens next.