5 pitfalls to avoid when managing a workplace investigation

A version of this article was first published in People Management in July 2025.

It’s no secret that workplace investigations can be tricky to manage and the consequences of getting it wrong can result in a host of issues for employers including employee distrust, reputational damage and employment tribunal claims. To help employers navigate workplace investigations successfully, we identify five common pitfalls when running a workplace investigation, and how to steer clear of them.

Losing sight of the end goal

The Pitfall: Your investigation starts to spiral out of control.

The Fix: It is not uncommon for an investigation to grow unnecessary arms and legs as the process unfolds. To prevent this from happening, take the time before the investigation starts to nail down the scope of what the investigation will cover – for example, where an employee has submitted an unwieldy grievance, look to clarify the key issues of concern with them and agree what will be investigated. Setting out the scope at the outset means that those involved will be clear on what will (and will not) be investigated.

For complex investigations, it can also be helpful to create an investigation plan setting out the issues to be investigated, the nature of the investigation required to respond to each allegation (including, for example, who will be interviewed and what other evidence will be considered), as well identifying a provisional timeline.

If new issues arise as the investigation progresses, reassess what you are trying to achieve to see if the new issues fall within the scope. If they do, amend the plan accordingly. This should help you keep control of the process and prevent the investigation from snowballing.

Delays that drag on

The Pitfall: The investigation takes so long that it leads to complaints by the employee(s) concerned that the process is unfair.

The Fix: This is an area where employers often come unstuck, particularly where there are a significant number of issues to be investigated and/or a number of people are involved. It’s important that the employer undertakes the necessary investigation to establish the facts, and so the process should not be rushed. However, unmanaged and prolonged delays risk jeopardising the fairness of the investigation – indeed the Acas Code of Practice on disciplinary and grievance procedures stipulates there should be no “unreasonable delay” when carrying out an investigation, so it is important to minimise the risk of delays.

When appointing an investigation manager, make sure the proposed individual has sufficient time to complete the investigation. Check holidays, workload and other commitments before making the appointment.

Creating an investigation timeline identifying any fixed timeframes (e.g. arising from your policies) can be helpful. If there are delays, for example if you’re waiting for evidence such as CCTV footage, or due to witness availability, communicate these to the employee so they are not left in the dark.

Delays can be particularly problematic where the employee under investigation has been suspended so every effort should be made to keep the investigation on track in these circumstances. If a delay is unavoidable, try to minimise the impact by progressing other areas of the investigation in the interim.

Over-reliance on HR

The Pitfall: The investigator doesn’t understand the role of HR.

The Fix: The investigator must be prepared to dedicate sufficient time to conduct the investigation and understand that they are responsible for the outcome – they are not just fronting it whilst HR does all the work!

HR’s involvement should be in a supporting capacity only. Whilst it is appropriate for HR to provide guidance on legal frameworks, policy, procedure, and best practice, they should not influence the investigator or nudge conclusions or decisions, otherwise the fairness of the investigation risks being called into question.

Failing to follow your own policies

The Pitfall: You don’t follow your internal policies, leaving your process open to challenge.

The Fix: Whilst it’s important to comply with the Acas Code, it is also essential to comply with your own policies. Before starting an investigation, the investigator should familiarise themselves with the relevant policies and guidance. These will include your disciplinary or grievance procedures, but may extend to others depending on the circumstances, for example, your anti-harassment policy. If the investigator needs to deviate from a policy, the reasons for this should be explained to the employee and documented.

Failure to comply with your policy (even if the policy is non-contractual) risks a challenge of unfairness from the employee. HR should offer support to the investigator to ensure that the investigation is free of procedural flaws.

Letting information slip

The Pitfall: Breaches of confidentiality that put the process at risk.

The Fix: Details of any investigation should only be shared on a “need-to-know” basis. Everyone involved, including witnesses, should be reminded that confidentiality is crucial, and failure to adhere to this could amount to a disciplinary offence.

Employees should be reminded that meetings should not generally be recorded, and discussions about the investigation (online or in person) must be avoided. Maintaining these boundaries is essential to protect the integrity of the process.

When dealing with a whistleblowing investigation, employers should be mindful of protecting the anonymity of the whistleblower. Careful planning of interview questions and compilation of the investigation report can help to prevent the whistleblower from being identified inadvertently.