How to run a workplace investigation
The investigation is where most disciplinary and grievance cases are won or lost. This is the method Acas sets out, with the points of law that catch employers out: who investigates, when to suspend, and who may bring a companion.
Before any disciplinary decision or grievance outcome, an employer must carry out a reasonable investigation to establish the facts. The Acas Code of Practice says necessary investigations should be carried out "without unreasonable delay", that in misconduct cases different people should carry out the investigation and the disciplinary hearing where practicable, and that an investigatory meeting should not by itself result in disciplinary action. Acas sets the process out in six steps. A tribunal can increase compensation by up to 25% where an employer unreasonably fails to follow the Code.
What are the steps in a workplace investigation?
Acas's step-by-step guide to investigations for discipline and grievance has six stages:
- Deciding to investigate. Is there something to look into, and is a formal process the right response? A quiet conversation resolves many minor issues.
- Preparing to investigate. Choose the investigator, write down exactly what is being investigated, and plan who to speak to and what records to gather.
- Carrying out an investigation. Collect the evidence: documents, messages, rotas, system logs, CCTV where you hold it lawfully.
- Holding investigation meetings with the person concerned and anyone else involved.
- If there are witnesses, take their accounts and ask them to confirm a written statement.
- After an investigation. Write the report and hand it to the person who will decide what happens next.
Acas is direct about why this matters: "If the employer does not carry out a reasonable investigation, any decisions they make in the disciplinary or grievance case are likely to be unfair."
Who should investigate?
Someone who is not involved in the matter and will not be deciding it. Paragraph 6 of the Acas Code says: "In misconduct cases, where practicable, different people should carry out the investigation and disciplinary hearing."
In a small company that can be hard. A workable arrangement is one manager to investigate, a second to hear the case and a third, usually the most senior person, held back for any appeal. If there are not three people, say so in your procedure and consider an outside investigator for serious cases. The investigator's job is to establish facts, not to prove the allegation.
What does the Acas Code say about investigations?
| Paragraph | What it says |
|---|---|
| 5 | "It is important to carry out necessary investigations of potential disciplinary matters without unreasonable delay to establish the facts of the case." |
| 6 | "In misconduct cases, where practicable, different people should carry out the investigation and disciplinary hearing." |
| 7 | "If there is an investigatory meeting this should not by itself result in any disciplinary action." |
| 8 | Any period of suspension with pay "should be as brief as possible, should be kept under review and it should be made clear that this suspension is not considered a disciplinary action." |
The Code is not law in itself, but tribunals take it into account, and under section 207A of the Trade Union and Labour Relations (Consolidation) Act 1992 a tribunal may increase an award "by no more than 25%" where the employer unreasonably failed to comply with it. The same section allows a reduction of up to 25% where the employee was the one who failed.
Should you suspend the employee?
Not as a matter of routine. Acas says "you should not use suspension automatically" and to "only suspend someone if there's no other option". Alternatives include a temporary change of duties, shift, site or reporting line, or working from home.
If you do suspend:
- It is not a punishment. Acas: "Suspension does not mean an employee has done anything wrong, and should not be used to discipline someone." Say so in the letter.
- Pay continues. "The suspended person should continue to get: their pay; any benefits in their contract".
- Keep it short and reviewed. "There is no minimum or maximum amount of time you should suspend someone for. But you should keep it as short a time as possible", and "You should review the suspension regularly".
- Stay in touch. Name a contact who is not the investigator, and think about the effect on the person's health.
Does the employee have the right to be accompanied?
Not at a disciplinary investigation meeting. The Code says: "there is no statutory right for an employee to be accompanied at a formal investigatory meeting, such a right may be allowed under an employer's own procedure." Acas adds that "it's good practice for employers to allow it". For a grievance, the legal right to be accompanied applies to any grievance meeting.
The statutory right does apply at the disciplinary hearing itself, where the worker may bring a colleague or a trade union representative. Many employers allow a companion at the investigation stage as well; if you do, write it into the procedure and apply it to everyone. Consider it in any case for someone who is young, unwell, disabled or not fluent in English.
How long should an investigation take?
There is no fixed period. Acas says "a simple case might only take a day to gather enough information. A more complicated case could take several weeks", that "the employer or person investigating should set a reasonable timescale and tell the worker", and that "while an investigation should be completed as quickly as possible, it always needs to be thorough and fair."
Start as soon as possible, because memories fade and CCTV is overwritten. If the timescale slips, tell the person why and give a new date; silence is what turns a delay into a grievance.
How do you run the meetings and write the report?
- Give notice of the meeting and say what it is about. An ambush produces a poor account and a later complaint.
- Ask open questions, then test the account against the documents. Put every allegation to the person and record their answer.
- Take notes and share them. Ask each person to confirm their notes or statement, and record any corrections.
- Follow up what they tell you. If the employee names a witness or a document that would help them, look at it. Evidence that points away from the allegation matters as much as evidence that supports it.
- Keep it confidential, and tell witnesses to do the same.
- Write a report with three parts: what was alleged, what the evidence shows on each point, including what could not be established, and whether there is a case to answer. The investigator does not decide the sanction.
If there is a case to answer, the next stage is a hearing under your disciplinary policy, run as the disciplinary procedure guide describes. For complaints, see the grievance procedure for employers. Whether the issue is conduct or capability changes the route; capability vs conduct explains the difference.
What goes wrong most often?
- The same manager investigates, decides and hears the appeal.
- Suspension on day one, by reflex, with no review date.
- The allegation changes between the investigation and the hearing.
- Only evidence against the employee is collected.
- Nothing is written down until the dismissal letter.
- Weeks pass with no contact.
Frequently asked questions
Is an investigation required before a disciplinary hearing?
Yes. The Acas Code of Practice says it is important to carry out necessary investigations of potential disciplinary matters without unreasonable delay to establish the facts. Acas says that without a reasonable investigation any decision is likely to be unfair.
Can the same person investigate and hold the disciplinary hearing?
The Acas Code says that in misconduct cases, where practicable, different people should carry out the investigation and the disciplinary hearing.
Is there a right to be accompanied at an investigation meeting?
There is no statutory right to be accompanied at a disciplinary investigation meeting, though an employer's own procedure may allow it and Acas says it is good practice. The legal right applies at disciplinary hearings and at grievance meetings.
Does a suspended employee get paid?
Acas says a suspended person should continue to get their pay and any benefits in their contract. Suspension should be as brief as possible, kept under review, and is not a disciplinary sanction.
How long should a workplace investigation take?
There is no fixed period. Acas says a simple case might take a day and a more complicated case several weeks, and that the employer should set a reasonable timescale and tell the worker.
What happens if an employer does not follow the Acas Code?
An employment tribunal may increase any award by up to 25% if the employer unreasonably failed to follow the Code, under section 207A of the Trade Union and Labour Relations (Consolidation) Act 1992.
Sources
Checked against the primary source on 5 October 2026.
- Acas: investigations for discipline and grievance, step by step - the six steps, timescales and the right to be accompanied
- Acas Code of Practice on disciplinary and grievance procedures - paragraphs 5 to 8
- Acas: suspension during an investigation - when to suspend, pay and review
- Trade Union and Labour Relations (Consolidation) Act 1992, s.207A - the adjustment of up to 25%
- Employment Relations Act 1999, s.10 - the right to be accompanied at a hearing
This is general guidance for UK employers and is not legal advice. Take advice on anything contested, unusual or expensive.
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