How To Conduct A Workplace Investigation In The UK: Step-By-Step Guide

When something goes wrong at work, it’s tempting to move quickly - especially in a small business where you know your team well and you need the issue resolved yesterday.

But if you skip steps (or rely on gut feel), you can accidentally turn a manageable workplace issue into a formal grievance, a tribunal claim, or a long-term morale problem.

This guide breaks down how to conduct a workplace investigation in a practical, UK-friendly way. It’s written for employers and managers who want a fair process, a clear paper trail, and a defensible outcome - without drowning in legal jargon.

Why A Proper Workplace Investigation Matters (Even In A Small Business)

A workplace investigation is a structured process to gather facts and evidence, so you can make a fair decision about what happened and what to do next.

In practice, investigations commonly happen when there are allegations of:

• Misconduct (e.g. rudeness to customers, breach of policies, insubordination, misuse of expenses)
• Serious misconduct (e.g. theft, violence, harassment, discrimination)
• Poor performance or capability concerns (where you need to understand causes and context)
• Bullying or harassment complaints
• Data breaches or confidentiality issues
• Health and safety incidents

For UK employers, a fair investigation is often the foundation of a fair process. If the matter later becomes a disciplinary issue or a dismissal, you’ll usually need to show you took reasonable steps to establish the facts first.

It’s also worth keeping the ACAS Code of Practice on disciplinary and grievance procedures in mind. Tribunals can increase or decrease certain awards by up to 25% where there’s an unreasonable failure to follow the Code, so aligning your investigation and any subsequent disciplinary/grievance steps with ACAS guidance is a sensible risk-management move.

Even if the issue never escalates, a solid investigation helps you:

• make consistent decisions (and avoid accusations of bias)
• protect team culture by showing you take concerns seriously
• reduce business disruption by reaching an outcome faster and with less conflict
• create an evidence trail in case the decision is challenged later

And yes - it can feel awkward investigating people you work closely with. That’s normal. The key is to follow a process that is calm, neutral and well documented.

Step-By-Step: How To Conduct An Investigation At Work

If you’re looking for a simple way to approach how to conduct an investigation at work, think of it as five phases: plan, gather, interview, assess, conclude.

1) Identify The Issue And Decide Whether An Investigation Is Needed

Start by clarifying what you’re dealing with. Not every workplace concern needs a full investigation, but you do need enough information to decide next steps.

Ask yourself:

• What exactly has been alleged (and by whom)?
• Is it misconduct, poor performance, a grievance, or a safety issue?
• Is there immediate risk (to people, property, customers, or data)?
• Do we need to take temporary action while we look into it?

If it’s likely to lead to a disciplinary outcome (or it’s serious), an investigation is usually sensible. If you’re unsure, getting your process aligned with your Staff Handbook (and any internal policies) is a good starting point.

2) Appoint An Investigator (And Keep It Neutral)

Choose someone who can be fair, calm, and objective - and who hasn’t been personally involved in the events.

In a small business, that can be tricky. If you don’t have a separate HR team, consider:

• a manager from a different area of the business
• a director who isn’t personally involved
• an external investigator (for sensitive allegations or senior staff)

Whoever you appoint should understand they’re not “proving guilt” - they’re gathering facts so the business can make a fair decision.

3) Consider Suspension Or Temporary Adjustments (Only If Necessary)

Sometimes you may need to separate people, protect evidence, or manage risk while you investigate.

That might involve:

• temporary changes to shifts or reporting lines
• temporary work-from-home arrangements (if appropriate)
• suspension (usually on full pay) in more serious cases

Suspension shouldn’t be treated as a punishment - it’s a neutral step to allow the process to run properly. It’s also an area where employers can make costly mistakes, so it’s worth checking your approach against practical best practice like Suspension guidance.

4) Define The Scope And Plan Your Evidence

Before you start interviewing people or pulling documents, write down a short investigation plan. This will save you time and help you stay consistent.

Your plan might include:

• allegations/issues to be investigated (be specific)
• time period covered (e.g. “events between 1–15 December”)
• people involved (complainant, respondent, witnesses)
• evidence sources you’ll review
• target timeline (with some flexibility)

If you’re unsure what a structured early-stage meeting looks like, the format used in a Fact-Finding Meeting is a useful benchmark.

5) Gather Evidence (Before You Rely On Memory)

Evidence gathering is where a lot of investigations fall down - not because the employer didn’t try, but because they didn’t preserve information early enough.

Depending on the issue, you may need to gather:

• written complaints or incident reports
• emails, Teams/Slack messages, or other work communications
• CCTV footage (if relevant and lawfully used)
• time records, rotas, access logs
• expenses claims or finance records
• policies and training records
• previous warnings or performance records (handle carefully)

Be mindful of data protection and confidentiality: only access and share what you need for the investigation, and keep it secure. If you’re reviewing CCTV, emails, messages or other monitoring data, make sure you have a clear lawful basis under UK GDPR, you’re acting consistently with your policies and privacy information provided to staff, and you’re only using what’s necessary and proportionate for the issue you’re investigating.

Running Investigation Meetings And Interviews (What To Ask And How To Keep It Fair)

Most workplace investigations come down to interviews: what people say happened, whether their accounts are consistent, and how they respond to evidence.

Who Should You Interview - And In What Order?

A common approach is:

1. The complainant (to clarify the allegation and identify evidence/witnesses)
2. Key witnesses (while memories are fresh)
3. The employee accused/respondent (once you have enough detail to ask clear questions)
4. Follow-up interviews if new evidence emerges

That said, the right order depends on the risk of evidence being lost and who is available.

How To Structure Your Questions

Try to keep questions open and fact-focused:

• “Talk me through what happened from the start.”
• “What did you see/hear directly?”
• “Where were you standing and who else was present?”
• “What happened next?”
• “Do you have any messages or documents that support your account?”

Avoid questions that sound like you’ve already reached a decision, such as “Why did you do it?” or “Do you admit it?” too early. If you need to put allegations directly, do it calmly and clearly, and allow time for the person to respond.

Do Employees Have The Right To Be Accompanied?

This often comes up. Investigation meetings are different from disciplinary hearings.

Whether someone can be accompanied at the investigation stage can depend on your policies and the circumstances. Many employers allow a support person where appropriate (especially for sensitive allegations), but it’s not always a legal requirement at the investigation stage in the same way it can be for disciplinary hearings.

The key is consistency and fairness. If you’re giving one person extra support, consider whether others should have similar support.

Take Proper Notes (And Confirm Them)

Always take notes of investigation meetings. After the meeting, you can send the notes to the interviewee to confirm they’re accurate (or to note corrections), but think carefully about what you share and when. For example, you may choose to share a written summary rather than full notes, or delay sharing where there’s a genuine risk of evidence being influenced or confidentiality being compromised. Whatever approach you take, apply it consistently and keep a clear record of your decision-making.

This isn’t just admin - it’s part of building a reliable record of your process.

Assessing The Evidence And Writing Your Investigation Report

Once you’ve gathered evidence and conducted interviews, you’ll need to assess what you’ve learned and record it in a clear outcome document.

Assessing Credibility Without “Playing Judge”

Workplace investigations aren’t criminal trials. You’re not trying to reach “beyond reasonable doubt”.

Instead, you’re trying to make a reasonable decision based on available evidence. Helpful credibility indicators include:

• Is the account consistent over time?
• Is it supported by independent evidence (documents, CCTV, multiple witnesses)?
• Does the person have a reason to exaggerate or minimise events?
• Is the timeline plausible?
• Are there clear gaps, or is the person simply unsure (which can be honest)?

It’s normal to have conflicting accounts. Your job is to weigh them fairly and explain why you reached your conclusion.

What To Include In An Investigation Report

A strong investigation report is structured and easy to follow. It typically covers:

• Background (what prompted the investigation)
• Scope (what issues were investigated and what wasn’t)
• Evidence reviewed (documents, footage, interviews)
• Summary of key facts (chronology helps)
• Findings (what you conclude happened, based on evidence)
• Recommendations (e.g. proceed to disciplinary, performance process, training, no further action)

Try to keep the tone neutral and factual. This is not the place for emotional language or speculation.

What Happens After The Investigation? (Disciplinary, PIPs, Grievances And Next Steps)

After the investigation, you generally land in one of these outcomes:

• No further action (the allegation isn’t upheld or there isn’t enough evidence)
• Informal management action (coaching, training, mediation, clarified expectations)
• Formal performance management (where the issue is capability rather than misconduct)
• Disciplinary process (where misconduct may have occurred)
• Other actions (policy changes, reporting obligations, safeguarding steps)

If It’s A Performance Issue: Consider A Proper PIP

Sometimes an investigation reveals the problem isn’t “bad behaviour” - it’s lack of training, unclear expectations, workload issues, or a genuine capability gap.

In those cases, moving straight into discipline can be the wrong fit. A structured performance process like Performance Improvement Plans can help you handle the issue fairly and give the employee a proper chance to improve.

If It’s Misconduct: Move To A Fair Disciplinary Process

If your investigation suggests misconduct may have happened, the next step is usually a disciplinary hearing.

At that point, it becomes even more important that:

• the allegations are set out clearly
• the employee has time to prepare
• the hearing is run by someone appropriate (and ideally not the investigator)
• you follow your own policies and apply them consistently

A common practical step is issuing a clear invite letter - and it needs to include the right information. If you want a simple structure to follow, Disciplinary Meeting guidance can help you avoid missing key details.

If the allegation is potentially very serious, make sure you’ve considered whether it could amount to gross misconduct and whether your documents support that approach. It’s often helpful to sanity-check against a checklist like Gross Misconduct best practice.

If Someone Raises A Grievance During The Process

It’s not unusual for an employee (either the complainant or the respondent) to raise a grievance during an investigation. For example, they might allege bias, victimisation, bullying, or procedural unfairness.

Don’t ignore it. You’ll need to decide whether:

• the grievance should be dealt with separately and in parallel, or
• it’s so intertwined that it needs to be handled as part of the same overall process

Timing matters too - if a grievance is raised late in the day, you still need to handle it sensibly, but you may also need to keep the original process moving. Being across Grievance Procedure time limits and expectations can help you plan.

Make Sure Your Contracts And Policies Back You Up

A well-run investigation is much easier when your business has clear rules in place from the start - for example, on acceptable workplace behaviour, confidentiality, use of systems, and disciplinary procedures.

That’s where your Employment Contract and policies do a lot of the heavy lifting. If your documents are vague or out of date, investigations can become messy because everyone has a different view of what the standards are.

Key Takeaways

• A workplace investigation is a fact-finding process - it helps you make a fair decision based on evidence, not assumptions.
• If you want to conduct a workplace investigation properly, focus on a clear plan: appoint a neutral investigator, define scope, gather evidence, interview key people, and document findings.
• Suspension and other temporary measures should be used carefully and neutrally, and only where genuinely necessary to manage risk or protect the process.
• Investigation interviews should be structured and fair, with open questions and careful note-taking.
• Your investigation report should clearly set out what you investigated, what evidence you reviewed, what you found, and what you recommend happens next.
• After an investigation, the next step might be no action, informal coaching, performance management, or a formal disciplinary process - and the “right” path depends on the facts.
• Having solid contracts and workplace policies in place from day one makes investigations smoother, faster, and easier to defend if challenged.

If you’d like help with a workplace investigation (or you want to tighten up your contracts and policies so you’re protected from day one), you can reach us at 08081347754 or team@sprintlaw.co.uk for a free, no-obligations chat.