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Internal investigations – An introductory guide for employers and HR professionals

Workplace investigations can be an emotive and time-sensitive part of an HR professional’s workload. From collecting evidence to meeting witnesses, conducting investigations requires both meticulous attention to detail and a thoughtful, empathetic approach. In this guide, we take you through all the essentials to help you plan and carry out a thorough and efficient investigation, together with some tips on best practices.

What are workplace investigations and why are they important?

In the HR context, a workplace investigation is an internal review of specific incidents, allegations or concerns within an organisation. They usually involve a member of HR or a senior manager meeting witnesses and gathering evidence with a view to preparing an investigation report. In essence, investigations are all about establishing the facts of a matter in a way that’s impartial and ultimately leads to some sort of resolution to whatever has happened.

Investigations are important because they help you manage and resolve sensitive workplace issues such as misconduct, grievances, harassment, and whistleblowing. Investigations also help you reduce the risk of legal claims under employment laws. For example, a reasonable investigation can help you show an employment tribunal that you adopted a fair process before dismissing an employee.

In disciplinary and grievance cases, investigations also help you comply with the ACAS Code of Practice on Disciplinary and Grievance Procedures ('ACAS Code'). An unreasonable failure to follow the ACAS Code can lead to adverse consequences in employment tribunals including an increase of up to 25% in compensation.

When might you need to carry out an investigation?

There are many situations in the workplace that require investigations. These include:

  • Workplace misconduct. This is a spectrum of poor employee behaviour ranging from more general misconduct (eg lateness to work, refusal to follow management orders) to more serious or ‘gross’ misconduct (eg theft, fraud, violence). An investigation is usually required to establish whether an employee is in fact guilty of misconduct. Where an investigation finds evidence of misconduct, this is typically treated as a disciplinary matter at a subsequent disciplinary hearing. If an employee has over two years’ service and you dismiss them for misconduct without any investigation into the misconduct, the dismissal will nearly always be unfair.
  • Workplace grievances. These are typically complaints that employees raise about the workplace or their working conditions. This could include complaints about their terms and conditions relating to pay and benefits, performance and promotion decisions or the behaviour of a colleague. A grievance investigation will normally involve reviewing the employee’s complaint and any allegations, speaking to witnesses and deciding whether or not to uphold the grievance with recommendations for further action.
  • Allegations of bullying, harassment and discrimination. These are particularly sensitive employee relations issues that employers should address through robust and timely investigations because of the impact on the individuals involved, as well as the potential for very costly employment law claims and reputational damage. In many cases, bullying, harassment and discrimination allegations will normally be set out in a grievance and, as such, can be handled under a grievance process. However, there are situations where employers can come across bullying, harassment and discrimination allegations inadvertently (eg during an exit interview) and they should still review them as part of an investigation. An investigation is required to establish whether there is evidence to uphold the allegations and whether any further action needs to be taken (eg disciplinary action against the accused employee or improvements to policies, procedures and company culture). Sexual harassment in particular has been very topical in recent years with a new mandatory duty to prevent sexual harassment coming into force in 2024 - employers would be wise to review and investigate any allegations of sexual harassment with a particularly fine toothcomb.
  • Whistleblowing. This is where an employee makes a protected disclosure about wrongdoing within their workplace (eg a criminal offence or health and safety risk). It’s important to fully investigate whistleblowing disclosures since these may alert you to genuine risks and liabilities within your business (eg a risk to life or financial irregularities). Employees are also protected from dismissal and detrimental treatment for making whistleblowing disclosures and claims in relation to these protections can be costly. A robust investigation can therefore help you show that you took the employee’s disclosures seriously and minimise the risks of whistleblowing related claims against you. Investigations also help you contain whistleblowing disclosures internally within your business and reduce the chances of an employee making an external disclosure (eg to a regulator or to the press) which could have serious regulatory and reputational consequences.

Is an investigation always needed?

Investigations can be labour and time intensive for HR teams and senior management. They also represent a significant escalation of a workplace issue that may inflame employee relations and harm team morale. It’s important to assess each situation carefully to determine if a formal investigation is necessary and whether there are alternative ways to resolve the matter.

For most disciplinary and grievance matters, the ACAS Code expects you to be able to address them informally and to explore mediation where possible. This is likely to be appropriate for less sensitive workplace matters that can be resolved through informal communication between employees and their line managers. This might include, for example, complaints and issues about simple payroll mistakes, an employee’s workload and working relationships within teams. Launching a full-scale investigation in these circumstances may be disproportionate when an informal conversation might be all that’s needed.

However, there are many situations where an informal approach is not recommended. These include allegations of serious workplace misconduct (eg theft, fraud, violence), all forms of bullying and harassment (including sexual harassment) and whistleblowing disclosures. In these cases, it’s best to try to proceed to a more formal process as quickly as possible.

How do you carry out an investigation?

How you conduct an investigation depends on the type of investigation needed (eg disciplinary, grievance or whistleblowing) and what your internal policies and procedures say. General guidance is provided for all investigations below, but we encourage you to speak to one of our employment law solicitors for advice on your specific investigation as additional requirements may apply in certain contexts (eg. FCA regulated firms):

  • Plan your investigation. Determine the type of investigation needed (eg grievance, misconduct, whistleblowing), and identify any key witnesses you will need to meet. Think about the type of evidence you’d like to collect (eg emails, instant messaging logs, documents, meeting minutes) and who within your organisation can help you access the evidence. Think about logistics for the investigation too. This could include administrative matters like whether meetings take place in person or remotely and witness availability, but also more nuanced matters such as the gender of the investigator for complaints of sexual harassment.
  • Define the scope of the investigation. It’s very important to set the boundaries of the investigation at the outset. This makes it easier to formulate questions for investigation meetings and to contain the investigation. A set of terms of reference for the investigator that clearly set out the scope of what they will be looking into can help avoid a situation in which the investigation takes on a life of its own - this is an issue that’s common for all clients, so try not to worry if it does happen.
  • Decide whether any immediate action is needed. Some matters that require investigation may raise such serious or sensitive issues that urgent action is needed as a preliminary step as part of the investigation planning. For example, you may need to carefully consider whether to reassign or suspend an employee accused of sexual harassment while the investigation is ongoing in order to protect the welfare of other employees. Alternatively, an employee raising a grievance about working conditions may have been signed off sick and need HR support.
  • Review internal policies and guidance. Check whether you have any internal policies covering the type of investigation you’re going to be carrying out (eg a grievance, disciplinary or whistleblowing policy). Get comfortable with the policy and check key information such as what it says about who should conduct the investigation and timeframes for completing it. In some cases, you may need to consult guidance like the ACAS Code (eg where you do not have an internal disciplinary or grievance procedure) or an employment solicitor if the investigation is likely to be complex.
  • Conduct a 'reasonable' investigation. At a minimum, this involves meeting all key witnesses including any employees raising complaints or concerns, any accused employees and any other obvious witnesses and establishing the facts. The investigator should try to stick to the original scope of the investigation. This will help them stay on track in terms of process and timing and avoid expanding the scope of the investigation. That said, investigations can often be fast-moving with new information coming to light. If any new information is relevant, it should be investigated and any critical witnesses interviewed. You should aim to keep employees involved in the investigation updated on timing. The investigation should be fair, impartial, and thorough, focusing on gathering relevant facts.
  • Maintain confidentiality. Think about how you will safeguard the confidentiality of the investigation. This means the confidentiality of the investigation itself, as well as the confidentiality of a complainant, the accused and any witnesses. As recognised by the ACAS guide to conducting workplace investigations, confidentiality helps protect individuals involved in the matter, maintains staff morale and avoids the risk of employees discussing or agreeing their evidence among each other. You should consider whether it’s possible to investigate a matter without revealing names to witnesses. If that’s not possible, then it’s good practice when holding investigation meetings to inform employees of their duties of confidentiality and to not discuss the investigation with anyone else.

Who should carry out the investigation?

You should check what any of your internal policies say about who should conduct the investigation. If your policies don’t specify who should act as the investigator, then ideally you should appoint someone within your business who is independent from the matters that are the subject of the investigation and with appropriate experience and training in carrying out investigations.

In most cases, investigators are senior members of HR, but can also be senior managers from other business units if the investigation relates to a specific function (eg finance). Although you will want to find someone sufficiently senior within your business to carry out the investigation, you may still need other appropriately senior staff later down the line to hear appeals or to act as a disciplinary hearing chairperson. For that reason, try not to find the most senior person within your business at the investigation stage.

You might also like to think about the specific characteristics of the investigator that could be helpful. In sexual harassment complaints, a female accuser may be more comfortable speaking to a female investigator than a male investigator. In discrimination complaints, it would be helpful for the investigator to have experience and training in diversity, equity and inclusion topics where possible.

There may be some cases where an external investigator is needed. It could be that your business does not have anyone with the necessary HR or investigation skills needed to carry out an investigation, or the subject matter of the investigation is exceptionally serious or sensitive and an independent external investigator is deemed more appropriate. Our employment solicitors are regularly instructed to act as independent external investigators so have a wealth of experience in conducting an investigation.  If you find yourself needing such support, then speak to one of our employment law solicitors

Who should you interview as part of the investigation and in what order?

You should arrange investigation meetings with all key employees involved in the subject matter of the investigation. In grievances and whistleblowing disclosures, this will involve meeting the employee making the complaint or disclosure and any other employees that have allegations made against them. In disciplinary cases, this would involve meeting the employee who is accused of misconduct and any witnesses to the misconduct. You should ideally meet the person making the complaint or disclosure first to record their version of events. You should then meet any witnesses that are relevant to the matter afterwards.

When thinking about who to interview as part of your investigation, you should balance the need to collect all relevant evidence against the need to try to contain the investigation as far as possible. It is not necessary to interview every potential witness if this will result in confidentiality breaking down or the scope of the investigation expanding significantly. Instead, focus on key witnesses and if their accounts are similar, that should be enough. At the same time, if new information comes to light during an investigation, you must interview any additional witnesses that could provide useful information. The most important thing is that you interview all obvious witnesses and you don’t leave anyone out that could significantly help the investigation.

What happens at an investigation meeting and how should you set them up?

Investigation meetings are an opportunity for an employee to provide their version of events and for the investigator to establish the facts. They should be neutral and focussed on establishing what happened. Importantly for disciplinary investigations, investigation meetings are not the same thing as a disciplinary hearing, meaning the investigator must not make accusations or give the impression that a particular outcome will apply. We suggest the following process for running investigations meetings:

  • Arrange the meeting. You should try to set up the investigation meeting as quickly as possible and in line with any specific timeframes in your workforce policies. You should give the employee notice of the time and place of the meeting and whether the employee has any right to be accompanied to the meeting under employment laws or the terms of your policies. Try to hold the meeting somewhere discreet if holding the meetings in-person. For disciplinary investigation meetings, it is often helpful not to let the accused know in advance that the meeting is an investigation meeting so you can witness their immediate response to the allegations against them. Please speak to one of our employment law solicitors to discuss this and similar tactics. 
  • Hold the meeting. At the meeting, the investigator should explain who they are and their role, the purpose of the meeting and set robust expectations around confidentiality. The investigator should emphasise the fact-finding nature of the meeting. The investigator should also explain that the employee’s witness statement from the meeting may be used in an investigation report and who will see it. Investigation meetings can be unsettling, particularly if an employee has never attended one before. The investigator should try to put the employee at ease by explaining that it is an investigation meeting only and not any other HR process such as a disciplinary hearing and give the employee the opportunity to ask any questions they may have throughout the meeting.
  • Establish the facts. The investigator should ask all relevant questions necessary for establishing the facts. The investigator should ask probing questions but should try to avoid coming across as hostile or adversarial. If the employee mentions specific evidence in support of their statements (eg emails and computer files, CCTV, physical documents), the investigator should try to obtain copies. Similarly, if the employee mentions specific employees, the investigator should consider whether to meet those employees as part of the investigation.
  • Take notes of the meeting. The investigator should record the employee’s responses as well as any refusal to respond to a question. The notes of the meeting can then be used to create a more formal witness statement or meeting note after the meeting. Witness statements do not need to be a verbatim record of the entire discussion, but they should broadly reflect what was discussed during the meeting. Once a witness statement is typed up, the investigator should share the statement with the employee who gave the statement and should ask the employee to sign the statement and / or agree that it is an accurate record of the conversation. You will need to have a process in place for agreeing any edit requests from an employee relating to their witness statement.

How do you make findings of fact as part of the investigation?

As mentioned, the main purpose of the investigation is to establish the facts. In an HR context, it is acceptable for the investigator to make findings of fact on a simple balance of probabilities (ie it is more likely than not that something happened). For example, if an employee claims that a colleague made inappropriate comments about them during a team meeting and at least one witness corroborates this claim, the investigator could decide on balance that this in fact happened. Where there is insufficient evidence to support the employee’s claim (eg it is simply the employee’s word against a colleague’s word), the investigator would need to indicate in the investigation report that there is insufficient evidence to make a finding of fact about the matter. Making findings of fact often requires a degree of judgement and so again, it’s helpful to have an investigator with investigation experience.

How should you report your investigation findings?

After completing the investigation, the investigator should report their findings in a well-structured investigation report. The report should include an introduction providing the background of the investigation, a summary of the investigation process and witnesses, which facts were established and which were not, and a conclusion with any recommendations for further action. Witness statements and evidence gathered as part of the investigation are usually attached to the investigation report.

One question clients often ask is how detailed the investigation report should be. Generally, the length and detail of a report should be proportionate to the complexity of the matter – ie an investigation into serious allegations of financial irregularity is likely to justify a very extensive and technical report compared to a straightforward grievance about an employee’s working hours. What’s most important is that the report establishes all of the relevant facts and is a neutral reflection of the investigator’s independent conclusions.

What should happen after the investigation?

After concluding the investigation and writing up the investigation report, there are still a number of steps that need to be completed before you can close down the investigation in full:

  • Making recommendations. The investigator may make recommendations in their investigation report. Typically, these might be recommendations for more formal or informal action or changes to policies and procedures. For example, in disciplinary investigations, the investigator might recommend that the employer takes more formal action through a disciplinary hearing to hear allegations of misconduct. It’s important that recommendations do not appear as sanctions or prejudgments. They should simply be guidance to the employer on next steps. If an investigation makes recommendations, you will need to take steps to act on them.
  • Sharing the investigation report. Investigation reports may need to be shared with key decision-makers within your business (eg to help a senior manager reach a decision on further action) but they must not be shared more widely. You might also need to deal with requests from individual employees to see the investigation report.  If an employee requests access to the investigation report or witness statements, under data protection laws they are entitled to see the parts of the report or witness statements that contain their personal data. That means you would need to share the parts of the report or witness statements that contain their name along with the context in which their name appears. You must not give them any part of the report that contains the personal data of any third party (eg another employee) without that third party’s consent. In practice, this means you would need to redact parts of the report or witness statements that contain third party personal data before sharing them with an employee.
  • Supporting the decision-maker. If the investigation leads to further action (eg a disciplinary hearing), the investigator may need to remain on hand to provide information and context to the decision maker in order to help them reach a decision.
  • Keeping adequate records. Keeping records of the investigation is vital as it will allow you to demonstrate the process you adopted to investigate relevant workplace issues should you ever have to produce evidence of such in an employment tribunal (eg to show that a subsequent dismissal of an employee was fair). You should securely store copies of meeting minutes, witness statements, the investigation report, emails with witnesses and evidence gathered as part of the investigation. Using password protection and encryption of documents is highly recommended to safeguard the confidentiality and secure document storage. Document retention and storage should comply with data protection laws, meaning you should retain them no longer than is necessary and in line with your document retention policies.

Top tips for handling workplace investigations

Investigations can seem daunting, but with the right planning and team they can be completed seamlessly in a way that resolves the issues at hand. We finish this guide with some of our top tips for running high-quality investigations:

  • Plan early. There can often be a temptation to start an investigation as soon as possible, but we recommend spending some time planning out the scope of the investigation and preparing questions for the interviews. This will help you remain focused on the key issues and avoid having to hold additional meetings. It will also help you contain the investigation and reduce the risk of confidential matters becoming known to your wider workforce.
  • Keep an open mind. Avoid making assumptions about the facts or individual employees. The purpose of the investigation is to impartially establish the facts, meaning a neutral approach that avoids giving the impression of hostility is best. If you find evidence along the way that contradicts something an employee said, you can always hold another meeting with the employee to discuss the matter in more detail. Try to focus on listening to what employees say during the meetings using a mixture of open and closed questions.
  • Support employees along the way. Investigations can be an emotionally charged experience for the employees involved in them. As an employer, you have a duty of care to protect the wellbeing of your employees. HR should support the investigation through regular check-ins with the employees involved and where possible provide access to workplace benefits such as employee counselling schemes. A well-run investigation also requires regular updates to employees on timing, particularly to employees raising serious issues around discrimination and harassment as they may be anxious about the outcome.
  • Train staff and seek legal advice where needed. Investigations can raise complex issues that touch on a range of employment law topics such as discrimination and whistleblowing. Employment law claims in these areas can be costly in terms of the potential damages and reputational consequences that can arise for the business. You will want to make sure your investigation thoroughly establishes all relevant facts, while at the same time anticipating any potential legal risks that could create exposure for your business as a result of findings from the investigation. Our employment law solicitors are on hand to advise on all aspects of workplace investigations and can provide training on best practices.

About our expert

Sally Gwilliam

Sally Gwilliam

Employment Partner
Sally joined the employment team in August 2021 as a senior employment solicitor and became a partner in October 2023. Sally qualified in 2004 at international law firm DLA Piper, and worked there for a further 11 years. There she gained excellent skills and experience in employment law working for medium and large businesses across multiple jurisdictions and on complex legal and strategic issues. Since 2015, Sally has worked for two smaller legal businesses where her client base changed to SMEs giving her a fantastic understanding of the differing needs and priorities of any size of business and in a wide range of sectors.

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