Guide to conducting a disciplinary investigation

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If you are considering conducting a disciplinary investigation, use this guide to help you carry it out it legally and effectively.

Why this guide is necessary

The purpose of the guide to conducting a disciplinary investigation is to provide a structured approach for employers or HR professionals to follow when investigating a potential employee misconduct or violation of company policies. The guide serves as a framework to ensure that the investigation is conducted in a fair, thorough, and impartial manner, and that all parties involved are treated with respect and dignity.

Additionally, a guide helps ensure that all relevant facts are gathered, documented, and analysed, and that the investigation complies with legal and regulatory requirements.

A well-conducted investigation can help protect the organisation from legal liabilities, and can also help to maintain a positive work environment and employee morale.

Here are some key UK employment legislation that govern the implementation of a guide to conducting a disciplinary investigation:

  • Employment Rights Act 1996: This Act sets out the statutory framework for disciplinary and grievance procedures, and requires employers to provide employees with a written statement of their disciplinary procedures.

  • ACAS Code of Practice on Disciplinary and Grievance Procedures: This Code provides practical guidance on how to handle disciplinary and grievance issues in the workplace, and sets out the basic principles of fairness and transparency that should underpin disciplinary investigations.

  • Data Protection Act 2018: This Act governs the collection, use, and storage of personal data, including data gathered during a disciplinary investigation. Employers must ensure that any data collected during an investigation is handled in accordance with the principles of data protection law.

  • Equality Act 2010: This Act prohibits discrimination on the grounds of protected characteristics, including age, gender, race, and disability. Employers must ensure that their disciplinary procedures do not discriminate against any employee or group of employees.

  • Human Rights Act 1998: This Act incorporates the European Convention on Human Rights into UK law, and requires employers to respect the rights of employees during a disciplinary investigation, including the right to a fair hearing and the right to privacy.

  • Trade Union and Labour Relations (Consolidation) Act 1992: This Act governs the relationship between employers and trade unions, and sets out the procedures for collective bargaining and consultation. Employers must ensure that their disciplinary procedures comply with the requirements of the Act.


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15 mins
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2006 words, 5 pages A4
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Date last reviewed
1 June 2024
guide to conducting a disciplinary investigation

Guide to conducting a disciplinary investigation

A disciplinary investigation is where your organisation needs to look further into the conduct of an employee, or to ascertain the facts surrounding an incident or allegation, prior to taking disciplinary action.

It is not always the case that a disciplinary investigation will result in a disciplinary hearing. The aim of the investigation is to establish whether there the employee has a case to answer.Specific examples of when a disciplinary investigation would be needed include, but are not limited to:

  • allegations of rudeness or poor behaviour;
  • allegations of poor time-keeping;
  • allegations of harassment or bullying;
  • an allegation that an employee was drunk or under the influence of drugs at work.

Generally, an investigation would be used where there is a question-mark over the facts surrounding a workplace allegation against an employee of some form of misconduct or inappropriate or unlawful behaviour.Even where an employee has already admitted that they have done something wrong, in many cases it will still be necessary to conduct an investigation in order fully to understand the circumstances and ensure that everyone involved is treated fairly. It can also assist the employer in deciding its next steps, and provide valuable evidence, both against the employee and in mitigation, for a disciplinary hearing.

The risks of mis-managing a disciplinary investigation

The minimum standard that the law expects employers to adhere to in carrying out a disciplinary investigation is the ACAS Code on Disciplinary and Grievance Procedures. The Code sets out practical advice on how to conduct a disciplinary investigation and an Employment Tribunal will expect to see an employer following it in most cases.As an employer, you must follow a fair procedure in deciding whether to hold a disciplinary hearing and, ultimately, to dismiss your employee.

If you do not carry out a reasonable investigation, this could give cause for tribunal claims, for example, if an investigation precipitated the dismissal of an employee, who then makes a claim for unfair dismissal.If a claim is made against you, an employment tribunal will also look at if you have unreasonably failed to follow the ACAS Code on disciplinary and grievance procedures. If the tribunal does find that you unreasonably failed to comply with a provision of the Code then it can increase the amount of the compensatory award made against you by 25%.

How to conduct a workplace investigation 

What are the key components of a fair and lawful investigation? 

Role of the investigating officer

The first step is to decide who should conduct the investigation.While there is no rule specifying who should carry out a disciplinary investigation, there are some basic principles that should be followed to maintain procedural fairness:

  • you should avoid choosing the person who will then conduct the disciplinary hearing itself;
  • you should avoid choosing anyone who is closely linked to the incident in question, for example, who would also appear as a witness in the disciplinary hearing;
  • you should appoint someone who has received training in how to conduct a disciplinary investigation; and
  • you should consider, in cases of high complexity or seriousness, appointing someone external to take on the roll.

The ACAS Code recognises that in small organisations there may be a limited number of managers within an organisation, making it hard to appoint a wholly unconnected person to conduct a disciplinary investigation. It recommends that this should be done “where practicable”. An alternative is to commission an external specialist, to preserve the objectivity and integrity of the investigation.

The investigating officer should check their organisation’s own policy to see if it makes provision as to the timing of the investigation. Either way, the investigator should communicate to the employee in question the way the investigation will be conducted and how long they think it will take. If the investigating officer finds during the course of the investigation that there will be a delay, this should be communicated to the employee under investigation with the reason why being given where possible.It should be remembered that the investigating officer’s role is to ascertain the facts in order to see if there is a case to answer. Their role is not to prove guilt, but to collect evidence from both sides to provide a balanced picture of events. 

Gathering evidence 

Evidence can take many forms, including:

  • emails
  • CCTV recordings
  • telephone recordings
  • attendance records
  • receipts
  • computer records
  • other paperwork

An investigating officer should note where evidence is missing and why it is missing.They should also understand the requirements of data protection law and respect an employee’s privacy. Ultimately, an investigatory officer does not have the same powers as the police and this should be understood by all involved.If an investigatory officer thinks that a search of an employee or their possessions is necessary, ACAS states that this should only be done in exceptional circumstances and where there is a clear, legitimate justification.

The reasons for, and results of, the search should be recorded immediately by the investigator. Where an investigator wishes to search an employee’s desk or workstation, they should ask the employee to be present. If the employee cannot be present then a manager should be asked to witness the search. 


An investigating officer must explain to witnesses that the matter under investigation and their involvement in it is confidential, and that a failure to maintain that confidence may in itself be a disciplinary offence.Sometimes, witnesses wish to remain anonymous. ACAS advises that this should be avoided if at all possible, as it puts the employee under investigation at a disadvantage if they do not know the nature of the evidence against them and who has provided it.

In exceptional circumstances, a witness statement can be anonymised. Such circumstances are where the witness has a genuine fear that they or their family will suffer intimidation or reprisals if they give evidence.If an investigatory officer decides that there is such a need for anonymity, they should still record the names of the witnesses as normal for their records, but redact the names and any other identifying features when presenting the evidence later.

The investigator should try to corroborate the anonymised evidence with evidence from an identified witness.It is important that the investigating officer does not guarantee anonymity to the witness, as, if the matter were to proceed to a court of law, the witness could be compelled to attend and give evidence. 

Investigatory interview

It is very likely that the investigation will involve meeting with the employee concerned, and witnesses. As far as the employee is concerned, there is no legal right to be accompanied by a colleague or a trade union representative to a disciplinary investigation meeting. However, it is considered good practice to allow the employee to be accompanied if they wish. You should check the policy of your organisation to see if it allows employees to be accompanied at this stage, and whether the right is extended to a friend, spouse or legal representative.At the meetings itself, the investigatory office can either take notes themselves, or have a note-taker attend the meeting for that purpose.

ACAS does not recommend that the meeting is recorded, either by video or audio, because this can be unnecessarily intimidating for the employee.The investigatory office is encouraged to ask probing questions, but at all times to remain courteous and bear in mind that the employee is may feel under considerable pressure and stress.Following the meeting, the investigating officer should send to the employee a copy of their own statement for them to check and approve. If the employee attempts to change their story, then this should of course be recorded by the investigating officer.

Questions to ask during an investigatory interview

Start by explaining who is in attendance and outline the format for the meeting. Explain that notes will be taken and the interviewee will be asked to check and sign these at the end of the meeting.Make it clear that honesty and confidentiality are expected from all parties at the meeting.Then explain the purpose of the investigation, and ask the interviewee to explain in their own words what happened. Keep the discussion focused on the facts and relevant to the allegations.Briefly summarise what you have understood from the interviewee’s statement and ask if they would like to add anything further. Then outline the next steps.

Outcome of the investigation

There are two possible outcomes after a disciplinary investigation. First, the employer may find that there is no case to answer. In that case, it is recommended that the employer writes to the employee to explain this and that the employee makes sure they retain this for their records. Alternatively, the investigator may find that as a result of their investigation, there is a case to answer and that the employee should appear before a disciplinary hearing to see whether a disciplinary sanction should be issued.In order to complete their investigation and make a recommendation as to whether there is a case to answer, the investigating officer may have to make a judgment as to where a particular incident took place.

The law does not require that the investigator’s findings reach the standard of proof required in criminal law, that is “beyond reasonable doubt.” An investigatory officer only needs to satisfy themselves on the “balance of probabilities” that an event did or did not take place (the civil law standard of proof).The investigator should report back to the individual or panel who are responsible for running the procedure as a whole. Occasionally, the investigator will recommend that there is no case to answer, but the employer will nevertheless proceed with a disciplinary hearing, or vice versa. Where this occurs, the reason(s) for the decision should of course be recorded by the employer.The outcome of the investigation must be communicated to the employee, whether or not they are completely exonerated, or the matter will proceed to a formal disciplinary hearing, or it is recommended for there to be mediation or training for those involved. 

Suspending employees during a disciplinary investigation

In some circumstance it may be necessary to suspend the employee under investigation. The ACAS Code states that if the employee is suspended, it must be on full pay, and the suspension be for as short a time as possible and kept under review.The suspension should be kept confidential and it should be made clear to the employee that their suspension is a neutral act and not a disciplinary sanction.It is good practice to hold a return to work meeting with an employee on their return to work after suspension in order to address any concerns they might have. 

Disciplinary investigation FAQs

Who should investigate a disciplinary?

A disciplinary should be investigated by someone unconnected with the matter. In other words, they would not have been required to appear as a witness themselves. They should also not be line-managed by the employees who are being investigated. Ideally, the investigator should also have had some training in how to conduct a disciplinary investigation.

How long can a disciplinary investigation last?

There is no set length for a disciplinary investigation. However, the investigation should be conducted promptly and an effort made not to prolong it beyond what is necessary, as the employee(s) in question will likely find the experience stressful. If an employer takes too long to conduct an investigation then this may result in an Employment Tribunal making a ruling that the procedure was unfair and in breach of the trust and confidence that an employer owes to its employees.

What is the difference between an investigation and a disciplinary?

An investigation happens first and will not necessarily result in a 'disciplinary'. The investigation is to establish the facts of what happened. A 'disciplinary' is short for a 'disciplinary hearing' which is a formal meeting at which evidence from the investigation is presented. The employee will have a chance to present their side of the story at the hearing and the person or panel conducting the hearing will decide whether to issue a disciplinary sanction and what that sanction will be.

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