How to Conduct a Workplace Investigation

from Silk Helix
Photograph of Jenefer Livings, Founder of Silk Helix Ltd
UPDATED 26 January 2024
First Published: 17 October 2023
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Workplace conflicts and disputes are inevitable, and when they arise, it’s crucial to handle them appropriately and in accordance with the law and when it comes to Disciplinary or Grievance investigations we should be following the ACAS code of disciplinary and grievance procedures.

What is the ACAS Code of Practice?

The Advisory, Conciliation, and Arbitration Service (ACAS) is a non-departmental public body in the UK that provides guidance and support on employment-related issues. The ACAS Code of Practice on Disciplinary and Grievance Procedures sets out principles and procedures for handling disciplinary and grievance matters in the workplace. While it’s not legally binding, employment tribunals will consider it when deciding relevant cases. Therefore, following this code is not just a good practice; it’s also essential to protect your business against potential legal disputes.

1. Fairness and Consistency

One of the fundamental principles emphasised by the ACAS Code of Practice is the need for fairness and consistency in handling disciplinary and grievance issues. To achieve this, consider the following:

  • Clear policies and procedures: Ensure that your organisation has clear and accessible policies and procedures for handling disciplinary and grievance matters. These policies should be communicated to all employees.

  • Equal treatment: Treat all employees equally and avoid any form of discrimination or bias during the investigation process. Base your decisions solely on evidence and facts.

  • Impartial investigators: Select investigators who are impartial and have no personal involvement in the case. This ensures objectivity and fairness.

2. Timeliness

The ACAS Code emphasises the importance of dealing with disciplinary and grievance issues promptly. Delaying investigations can result in increased stress and tension in the workplace. As soon as you become aware of a disciplinary or grievance issue, start the investigation process without undue delay. Make a plan for the investigation, and communicate these timescales, plus any changes, to all parties involved.

3. Preparation

It’s crucial to adequately plan your investigation. Consider what evidence may be available such as relevant documents, statements and records as well as identifying witnesses. There is a balance to consider in witnesses between not breaching confidentiality by involving people who wouldn’t otherwise be aware and making sure your investigation is full and thorough.

4. Impartiality and Confidentiality

Maintaining the trust of both the complainant and the accused is paramount. To ensure impartiality and confidentiality:

  • Maintain confidentiality: Keep all information related to the investigation confidential to protect the parties involved and prevent potential leaks.

  • Avoid conflicts of interest: Investigators should have no personal or professional conflicts of interest that could compromise their impartiality.

  • Communicate effectively: Keep all parties informed of the progress of the investigation within the boundaries of confidentiality. Maintain transparency while respecting privacy.

5. Interviews and Statements

Conducting effective interviews and gathering statements is a critical aspect of any investigation. To ensure a thorough and objective process:

  • Plan interviews: Prepare a list of questions and topics to cover during interviews with the complainant, the accused, and witnesses. Be prepared to divert from this list, to listen to responses and ask follow up questions as needed.

  • Use open-ended questions: Ask open-ended questions that encourage detailed responses and avoid leading questions that could bias the information gathered. This may be a good reason for using interviews over statements as they allow you to follow up and clarify information given.

  • Document everything: Keep detailed records of interviews, statements, and any other evidence collected. These records may be essential in future proceedings.

6. Reaching a Conclusion

In a Disciplinary situation in particular, the purpose of the investigation is to gather the facts, a conclusion may be that formal disciplinary action should be considered but that part is handed over to a Manager who has the authority to chair a disciplinary hearing and issue a relevant warning or decide to dismiss. It is not the role of the investigator to make this decision.

In a grievance and other situations the investigator may also be the decision maker, in all cases decisions must be made on the evidence and facts presented, ensuring that it aligns with your organisation’s policies and the ACAS Code. The investigation should outline mitigating factors that should be taken into account before any decision is made.


Effectively conducting investigations in compliance with the ACAS Code of Practice on Disciplinary and Grievance Procedures is essential for ensuring a fair process and particularly when it comes to avoiding claims of unfair dismissal. By following the principles outlined in the code—fairness, consistency, timeliness, impartiality, and confidentiality—you can navigate workplace disputes with confidence. Remember that the ultimate goal of these investigations is not just to resolve conflicts but also to maintain a positive and productive work environment for all employees.

While this guide covers the basics, every situation has its own complexities so you should always seek professional advice.
We can help, so book a Free Advice Call .

Article last updated: 26 January 2024

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