Workplace Investigation: A Step-by-Step Guide | CoachScript

A workplace investigation is the essential first step before any disciplinary hearing or formal grievance process — get it wrong and you risk an unfair dismissal claim, an employment tribunal, and a compensation uplift of up to 25% for failing to follow the ACAS Code of Practice. This step-by-step checklist is designed to help UK retail line managers run a fair, thorough, and legally defensible workplace investigation, even without a dedicated HR department behind you.

When does a workplace investigation need to happen?

Not every workplace issue needs a formal investigation. Minor concerns can often be resolved through a conversation or an informal performance discussion. However, you should launch a formal workplace investigation when:

• An allegation of misconduct has been made — for example, theft, harassment, bullying, or fraud
• An employee raises a formal grievance that cannot be resolved informally
• A serious incident has occurred on the shop floor or back office that requires the facts to be established
• You are considering whether a matter warrants a formal disciplinary hearing

The ACAS Code of Practice requires employers to investigate before taking formal disciplinary action. Skipping this step — even if you feel the outcome is obvious — is one of the most common reasons employment tribunals rule against employers.

Step-by-step workplace investigation checklist

Use this checklist to structure your investigation from the moment an issue is reported to the point where you hand your findings to the decision-maker.

Step 1: Decide whether a formal investigation is needed

• ☐ Assess the seriousness and complexity of the allegation
• ☐ Consider whether informal resolution is more appropriate first
• ☐ If formal, notify your line manager or HR adviser (if available) that an investigation is starting

Step 2: Appoint an impartial investigator

• ☐ Choose someone who is not involved in the incident and has no conflict of interest
• ☐ For serious matters (gross misconduct, discrimination), use a more senior manager
• ☐ Ensure the investigator is not the same person who will chair the disciplinary hearing — ACAS strongly recommends keeping these roles separate
• ☐ Brief the investigator on their role: fact-finding only, not determining guilt

Step 3: Set the terms of reference

• ☐ Define the scope — what allegations or issues are being investigated?
• ☐ Set a realistic timeline (ACAS advises completing investigations without unreasonable delay)
• ☐ Confirm what format the report should take and who receives it
• ☐ Establish whether recommendations are required alongside findings

Step 4: Consider suspension (carefully)

• ☐ Only suspend if necessary — for example, to protect witnesses, prevent evidence tampering, or protect the business
• ☐ Treat suspension as a neutral act, not a punishment — communicate this clearly to the employee in writing
• ☐ Keep suspension on full pay and review it regularly
• ☐ Keep the period as short as possible; prolonged suspension without progress can itself be challenged

Step 5: Notify the subject of the investigation

• ☐ Inform the employee that an investigation is taking place, what it concerns, and what the process will involve
• ☐ Do this promptly — unless there is a genuine risk that doing so would allow evidence to be destroyed
• ☐ Remind them of the duty of confidentiality and that breaching it may be a disciplinary matter in itself

Step 6: Gather evidence

• ☐ Collect physical evidence first: CCTV footage, EPOS transaction records, rota logs, email threads, messaging records, written communications
• ☐ Identify witnesses and decide who to interview
• ☐ Look for evidence that both supports and contradicts the allegation — your job is to establish the facts, not build a prosecution
• ☐ Keep a secure record of all evidence gathered, noting date and source

Step 7: Conduct investigation meetings

• ☐ Interview witnesses and the subject employee separately
• ☐ Remind everyone at the start that the meeting is fact-finding only, not a disciplinary hearing
• ☐ Note: there is no statutory right to be accompanied at an investigatory meeting, but consider allowing it, especially if the employee has a disability or is particularly vulnerable
• ☐ Use open questions: "Can you walk me through what happened?", "What did you see?", "Who else was present?"
• ☐ Avoid leading questions or anything that implies a predetermined outcome
• ☐ Take detailed notes and ask participants to sign them as an accurate record

Step 8: Write the investigation report

• ☐ Summarise the terms of reference and what evidence was gathered
• ☐ Present the evidence objectively — include both sides
• ☐ State your findings on the balance of probabilities: "It is more likely than not that…"
• ☐ Conclude whether there is a case to answer and, if required by your terms of reference, make recommendations
• ☐ Do not recommend a specific disciplinary outcome — that is for the hearing manager to decide

Common mistakes that lead to tribunal claims

Employment tribunals see the same procedural errors again and again. Avoiding these pitfalls is as important as following the positive steps above.

Mistake	Why it matters
Pre-judging the outcome	If the investigator signals guilt before facts are established, the entire process is tainted — tribunals take this very seriously
Vague allegations	Employees must know specifically what they are alleged to have done; a woolly allegation prevents a meaningful defence
Using suspension as a default	Suspension without clear justification has been found by tribunals to be a breach of trust and confidence, potentially entitling an employee to resign and claim constructive dismissal
Same person investigates and chairs the hearing	ACAS recommends separation of roles wherever practicable; failing this in serious cases suggests unfairness
Poor or missing records	Without contemporaneous notes, witness statements, and a written report, the employer cannot demonstrate that a reasonable investigation took place
Unreasonable delay	Prolonged investigations cause distress to all parties and suggest a lack of seriousness — ACAS expects reasonable speed

Using CoachScript to prepare for what comes next

Once your investigation is complete and you have established a case to answer, the next stage is a formal disciplinary or grievance hearing. CoachScript’s workplace investigation guide walks you through each stage of the process, and the script generator helps you prepare the hearing itself — from the invitation letter through to the outcome conversation — so you go in confident and legally compliant.

Frequently asked questions

Does an employee have the right to be accompanied at a workplace investigation meeting?

There is no statutory right to be accompanied at a purely investigatory meeting (as distinct from a disciplinary or grievance hearing). However, many employers permit it as good practice, and if the employee has a disability, denying a reasonable adjustment — such as bringing a support person — could lead to a discrimination claim under the Equality Act 2010. Check your own policy, and when in doubt, allow it.

How long should a workplace investigation take?

There is no fixed legal timeframe. ACAS requires investigations to be completed "without unreasonable delay." In practice, a straightforward matter should be wrapped up within two to four weeks. Complex cases involving multiple witnesses or significant evidence review may take longer, but you should keep all parties updated on progress and reasons for any delay.

Can I investigate misconduct and grievance issues at the same time?

Yes. If an employee raises a grievance mid-disciplinary — a common tactic — the ACAS Code allows you to pause the disciplinary to address the grievance, or to handle both simultaneously if they are closely related. The key is to document your reasoning clearly and ensure neither process prejudices the other.

What standard of proof applies to workplace investigations?

The civil standard: the balance of probabilities. This means you need to be satisfied that it is more likely than not that the alleged incident occurred. You do not need to prove it beyond reasonable doubt — that is the criminal standard. A thorough, objective investigation that weighs all available evidence will satisfy this test.

What should I do if a witness refuses to cooperate?

You cannot force an employee to participate in a workplace investigation, but you can note their refusal in your report and draw reasonable inferences from the evidence you do have. If a witness is also an employee and their refusal is itself obstructive, that may be a separate conduct matter. Document every attempt to engage them and your response.

A well-run workplace investigation protects both the business and the employee — it is not a process to rush through or cut corners on. If you need support preparing for what comes next, explore the ACAS process templates on CoachScript to ensure every stage is handled correctly.