Workplace Investigations
An investigation is not a finding. It is a fact-gathering exercise. But it rarely feels that way when you’re the one being investigated.
Your employer has a duty to investigate allegations thoroughly, impartially, and within a reasonable timeframe. The outcome of that investigation determines what happens next — whether the matter is dropped, referred to a disciplinary hearing, or resolved informally.
The quality of the investigation matters. A biased investigation produces a biased outcome. A rushed investigation misses evidence. A poorly scoped investigation asks the wrong questions. We make sure none of those things happen unchallenged.
How we support you
We review the scope of the investigation — what’s being alleged, who’s investigating, and whether the terms of reference are fair.
If you’re asked to attend an investigatory meeting, we advise you on your rights. While the statutory right to accompaniment applies to disciplinary and grievance hearings, many employers extend it to investigation meetings — and we push for that right where it isn’t offered.
We check that the investigation is conducted impartially, that evidence is gathered from all relevant sources, and that the outcome letter accurately reflects what was discussed.
If the investigation leads to a disciplinary hearing, your rep carries the full picture into that hearing. Nothing is lost between stages.
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An investigation is the fact-finding stage that comes before any formal action at work. Your employer gathers evidence, speaks to witnesses, and decides whether there is a case to answer. It is not a trial, and it is not the point at which anyone should be deciding your guilt. But what happens during the investigation shapes everything that follows — the disciplinary charge, the outcome, and your position if the case ever reaches a tribunal. This guide sets out what your employer must do, what they must not do, and how to protect yourself at each stage.
Contents
- What is a workplace investigation?
- When your employer should investigate
- What the law and the ACAS Code require
- Who can investigate
- The stages of an investigation
- Your rights during an investigation
- Suspension during an investigation
- Evidence, witnesses and confidentiality
- The investigation report and what happens next
- When an investigation is unfair
- FAQs
- How the National Employees Union can help
What is a workplace investigation?
A workplace investigation is a structured process for establishing the facts about an allegation. It can follow a complaint about your conduct, a grievance you have raised, a concern reported by a colleague, or an issue picked up through monitoring or audit.
The purpose is narrow. The investigator collects information so that someone else can decide whether formal action is needed. The investigator does not impose sanctions and should not reach a verdict on whether you should be dismissed.
That separation matters because it protects the fairness of the whole process. If the person who gathers the evidence also decides the outcome, the decision is contaminated before the hearing begins.
When your employer should investigate
ACAS guidance is clear that employers should carry out a reasonable investigation before taking any formal disciplinary or grievance action. The scale of the investigation should match the seriousness of the allegation.
A minor timekeeping issue may need a short conversation and a look at the records. An allegation of theft, violence or fraud needs a full investigation with witness statements and documentary evidence, because the potential outcome is dismissal.
Not every problem needs a formal investigation at all. Where the facts are undisputed and the issue is minor, an informal conversation is often the proportionate response. Your employer should not use a formal investigation as a pressure tactic when a quiet word would do. If they escalate anyway, the wider framework in our complete guide to disciplinary and grievance procedures explains how the stages fit together.
What the law and the ACAS Code require
There is no single statute that sets out how an investigation must be run. The requirements come from three sources working together.
The first is the ACAS Code of Practice on disciplinary and grievance procedures. The Code requires employers to carry out necessary investigations without unreasonable delay, to inform the employee of the problem in writing, and to hold a meeting before any decision. Tribunals take the Code into account, and an unreasonable failure to follow it can increase or reduce compensation by up to 25 per cent under section 207A of the Trade Union and Labour Relations (Consolidation) Act 1992.
The second is the law of unfair dismissal in the Employment Rights Act 1996. Section 98(4) asks whether the employer acted reasonably in treating the reason as sufficient for dismissal. In misconduct cases, that includes whether the employer held a genuine belief in the misconduct, on reasonable grounds, after a reasonable investigation.
The third is data protection law. Investigation files contain your personal data, so your employer must handle them lawfully, keep them secure, and retain them no longer than necessary.
Two changes are worth noting for 2026. Tribunal time limits for most claims rise from three months to six months for acts or omissions occurring on or after 1 October 2026. And from 1 January 2027, the qualifying period for ordinary unfair dismissal drops from two years to six months, which means far more employees will be able to challenge a dismissal that follows a defective investigation.
Who can investigate
The investigator should be impartial. In practice that means someone who has not witnessed the incident, has not already formed a view, and is not the person who will chair the hearing or the appeal.
| Role | Who should do it | Why |
|---|---|---|
| Investigator | A manager unconnected to the allegation | Gathers facts without a stake in the outcome |
| Disciplinary chair | A different, more senior manager | Decides on the evidence with an open mind |
| Appeal chair | A third manager, senior to the chair | Provides a genuine review, not a rubber stamp |
| Note-taker | An HR officer or administrator | Produces an accurate record for all parties |
| Your companion | A union rep or colleague | Supports you and checks the process |
In a small organisation, complete separation is not always possible. Tribunals accept that, but the employer must still show they did what was reasonable in their circumstances — for example by bringing in an external investigator or a director from another site.
The stages of an investigation
Deciding to investigate
Your employer should identify the specific allegation, decide the scope, and set a realistic timeframe. Vague investigations that roam across your whole employment history are a warning sign.
Telling you
You should be told that an investigation has started, what it concerns, and roughly how long it will take. ACAS guidance says this should happen as soon as the decision to investigate is made. Being kept in the dark for weeks is not a neutral act — it damages your ability to gather your own evidence.
Gathering evidence
The investigator collects documents, records, CCTV, emails, rotas or system logs, and takes statements. They should look for evidence that supports your account as well as evidence against you.
Investigation meetings
You will usually be invited to an investigation meeting to give your account. Our guide to what to expect at an investigation meeting explains how to prepare, what to say, and how to handle questions you cannot answer on the spot.
Reporting
The investigator writes a report setting out the evidence and a recommendation on whether there is a case to answer. The decision on formal action belongs to someone else.
Your rights during an investigation
You have fewer formal statutory rights at the investigation stage than at a hearing, but you are not without protection.
You have the right to be told what is alleged against you. You have the right to give your account before any decision is taken. You have the right to have your evidence and your suggested witnesses properly considered. You have the right not to be treated less favourably because of a protected characteristic, and not to be penalised for raising a grievance, blowing the whistle or taking part in union activities.
The statutory right to be accompanied under section 10 of the Employment Relations Act 1999 applies to disciplinary and grievance hearings, not to investigation meetings. Many employers allow a companion anyway, and many policies grant the right contractually. Always ask, and always check your policy. If your employer refuses and the meeting starts to look like a disciplinary hearing in disguise, say so on the record, because that shifts the meeting’s true character.
If the investigation moves to a formal stage, the right to be accompanied does apply, and our guide on preparing for a disciplinary hearing at work sets out how to use it.
Suspension during an investigation
Suspension is not a punishment and should never be automatic. ACAS guidance says it should only be considered where it is genuinely necessary — for example to protect the investigation, other staff, or the business, or to comply with a legal requirement.
Your employer should consider alternatives first: moving you to another team, changing your duties, restricting system access, or altering your shifts. They should keep the suspension under review and end it as soon as it is no longer needed.
Suspension should normally be on full pay. Unpaid suspension is only lawful where your contract expressly allows it, and even then it carries a high risk of a breach of contract or unlawful deduction claim. If you have been sent home pending an investigation, read our guide on your rights when you are suspended from work before you agree to anything.
Long, unexplained suspensions do real damage. Where a suspension drags on without reason, it can undermine the trust and confidence at the heart of your contract.
Evidence, witnesses and confidentiality
Witnesses should be interviewed promptly and separately, and asked open questions. Statements should be signed and dated. Where a witness needs anonymity because of a genuine fear of reprisal, the employer can anonymise the statement, but they must still give you enough detail to answer the allegation.
You are entitled to see the evidence being used against you before the disciplinary hearing. Withholding key documents until the hearing itself is one of the most common procedural failures employers make.
Confidentiality runs both ways. Your employer should not discuss the investigation with people who have no need to know. You should keep your own discussions limited to your companion, your union and your advisers. Contacting witnesses directly can look like interference, even when your intention is innocent.
If the investigation stems from a complaint you raised, keep your own written record of what you reported and when. Our guide to writing a grievance letter, with a template, shows how to set out the facts clearly so the investigator cannot mistake your position.
The investigation report and what happens next
The report should summarise the allegation, the evidence gathered, the accounts given, and the investigator’s conclusion on whether there is a case to answer. There are three usual outcomes.
| Outcome | What it means | Your next step |
|---|---|---|
| No case to answer | The evidence does not support formal action | Ask for written confirmation and for the file to be closed |
| Informal action | The concern is minor and can be resolved with a conversation or training | Check that no formal warning is recorded |
| Case to answer | The matter goes to a disciplinary hearing | Request the evidence pack and prepare your response |
You should receive a copy of the report, or at minimum the evidence relied on, in good time before any hearing. If your employer refuses to share it, ask in writing and keep the reply.
When an investigation is unfair
An investigation falls short when the employer decides the outcome first and gathers evidence to fit it. Other common failures include ignoring evidence that supports you, refusing to interview your witnesses, allowing the same manager to investigate and decide, drifting for months without explanation, changing the allegation part-way through, or relying on anonymous claims you were never shown.
None of these gives you a standalone claim on its own. Their effect comes later: a defective investigation makes any resulting dismissal procedurally unfair, and our guide on unfair dismissal and how to fight it explains how tribunals assess that. Raise your concerns in writing at the time, because a contemporaneous objection carries far more weight than one raised months afterwards.
FAQs
Do I have the right to be accompanied at an investigation meeting?
Not automatically. The statutory right under section 10 of the Employment Relations Act 1999 covers disciplinary and grievance hearings, not investigations. Many employer policies and union recognition agreements go further, so check your policy and ask anyway. If the meeting could lead directly to a sanction, argue that it is a disciplinary hearing in substance.
How long can a workplace investigation take?
There is no fixed legal limit. The ACAS Code requires employers to act without unreasonable delay, and most straightforward investigations conclude within two to four weeks. Complex cases involving multiple witnesses take longer. Ask for a timeframe in writing and chase it if it slips.
Can I refuse to attend an investigation meeting?
You can, but it rarely helps. Your employer can proceed on the evidence available, and your silence may be recorded as a refusal to cooperate. If you are unwell or need more time to prepare, ask for a short postponement in writing. Give a reason and propose an alternative date.
Can I be dismissed straight after an investigation?
No. The investigation only establishes whether there is a case to answer. Dismissal can only follow a disciplinary hearing at which you have been told the allegation, shown the evidence, and given a chance to respond. Skipping that stage makes the dismissal unfair.
Am I entitled to see the witness statements?
You should see the evidence relied on against you before the disciplinary hearing, including witness statements. Your employer can anonymise a statement where a witness has a genuine fear of reprisal, but they must still give you the substance of the allegation. You can also make a subject access request for your personal data.
What if the investigation was triggered by my grievance?
Your grievance should be investigated on its merits by an impartial manager. If disciplinary action against you appears only after you raise a complaint, record the sequence of events carefully. Retaliation for asserting a statutory right or for whistleblowing is treated seriously by tribunals.
How the National Employees Union can help
An investigation is the stage where cases are won or lost. Getting the facts recorded properly at the start is far easier than correcting them at a hearing.
National Employees Union members get a legally trained rep who will review the allegation and your employer’s policy, help you prepare your account and identify the evidence and witnesses that support it, attend meetings where your employer permits accompaniment, challenge unnecessary or unpaid suspension, press for disclosure of the investigation report and evidence, and represent you if the matter moves to a disciplinary hearing or beyond.
Time limits are strict, and they are changing. Contact us as soon as an investigation is mentioned rather than after the outcome lands.
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Written by the National Employees Union team. We support employees through workplace investigations across the UK. This guide is reviewed regularly and was last updated in August 2026. For advice on your specific situation, contact us.