Carrying out investigations in the workplace

Problems can arise in any workplace and making sure they are dealt with fairly and consistently may require an investigation. A properly conducted investigation allows an employer to fully consider the matter and then make an informed decision on it.

Key points

  • An investigation is a fact-finding exercise to collect all the relevant information on a matter.
  • An investigator should be given clear guidance on what exactly they are required to investigate, and how their findings should be reported.
  • Whenever possible the investigator should not be involved in the issue being investigated.
  • The investigator should gather and document what the issues of the matter are, consider what evidence may be available and relevant, and how it may be collected.

View or download the Acas guide on pdf icon Conducting workplace investigations [378kb]. Alternatively you can download our free investigations templates and letters below:

word icon Investigation Plan [17kb]

word icon Investigation Report [20kb]

word icon Letter informing employee they are subject of an investigation [29kb]

word icon Letter inviting an employee to an investigation meeting [28kb]


Find out how a simple case of theft turned into a bigger problem in our workplace investigations video.



When may an investigation be necessary?

Most matters that arise in a workplace can be resolved informally and quickly. If an informal resolution is not possible, then an investigation may be necessary if formal action is needed, such as a written warning.

Common situations that will often require an investigation include:

  • receiving a grievance from an employee
  • allegations of bullying and harassment
  • potential disciplinary matters against an employee
  • concerns over company policies and procedures.

Why is a properly conducted investigation important?

Investigations are an essential part of handling certain matters within an organisation. In potential disciplinary investigations a flawed or incomplete investigation can undermine the disciplinary process and leave employers vulnerable to claims for unfair dismissal.

If an employer dismisses an employee they must be able to show that they:

  • genuinely believed that misconduct had occurred
  • had reasonable grounds for this belief
  • had arrived at this belief after a reasonable investigation.

For a dismissal to be fair an employer must be able to show that they came to their decision as a result of a fair and thorough investigation.

Investigations are just as important when a grievance has been raised.  Where the grievance is not upheld, the evidence collected during the investigation can be used to explain the reasons behind this and show an employee that their grievance was taken seriously.

What is an investigator's role?

An investigator should try to be fair and objective when carrying out an investigation. They should look for evidence that supports and undermines the allegations.

Wherever practical an investigator should be:

  • available during the investigation's expected timeframe
  • not personally involved in the matter being investigated
  • not involved in any subsequent decision making on the matter
  • be trained in how to conduct an investigation.

When conducting an investigation, an investigator should:

  • consider what the issues of the matter under investigation are
  • plan how the investigation will be conducted
  • decide in what order evidence will be collected
  • collect all relevant evidence and consider what the evidence shows
  • report their findings.

What should an investigation include?

An investigator should be given details that set out exactly what they are expected to investigate. Their investigation should aim to establish the facts of the matter by collecting relevant evidence, such as witness statements, written documents and physical evidence and drawing a conclusion.

How much investigation is required and how it should be approached will vary from matter to matter. A complicated matter may take several weeks to conduct properly. A relatively simple matter may only require a small amount of investigation for it to be reasonable.

Acas conducting investigations training

Acas has scheduled Conducting investigations training sessions for employers, managers and anyone who may be ask to take on the role of investigator to help them better understand how to conduct a fair and thorough investigation.

The training covers how to conduct and manage a fair internal investigation, from gathering and assessing evidence through to presenting findings.