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How to Carry Out a Disciplinary or Grievance Investigation in the Workplace in the UK

Summary

  • A tribunal applies the band of reasonable responses to your investigation itself, so it asks whether a reasonable employer could have investigated this way rather than whether you reached the right answer.
  • Suspend only as a last resort, on full pay, after you have considered and documented alternatives such as redeployment or adjusted duties.
  • Your employee has no right to be accompanied at an investigation meeting, but they do hold that right at a disciplinary hearing that could result in a warning or other disciplinary action.
  • From 30 October 2026 the duty to prevent sexual harassment rises from taking reasonable steps to taking all reasonable steps, and liability for third-party harassment extends across every protected characteristic rather than sexual harassment alone, so an investigation into a harassment grievance should record what prevention measures you had in place at the time of the alleged incident.
  • From 1 January 2027, employees qualify to claim unfair dismissal after six months rather than two years, so investigate a short-service employee with the same rigour you would apply to a long-serving one.

Tips for Businesses

Write an investigation plan before you start, listing the allegations, the evidence you need and who you will interview. Record every decision, including the lines of enquiry you chose not to follow and why. Ask each witness to sign their statement. Keep the investigator separate from whoever will chair the hearing. If you need help running an investigation, our experienced employment lawyers can assist. Call 0808 258 4780.

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As an employer, you may need to carry out disciplinary or grievance procedures in the workplace. However, before deciding if this is necessary, you need to carry out an investigation. Your workplace policy or procedure regarding disciplinary and grievance procedures must be fair. It should follow the ACAS Code of practice on disciplinary and grievance procedures, which includes the need for an investigation process. This is especially important because if you face an employment tribunal, it will consider whether you followed the ACAS Code. This article will explain what you, as an employer, need to know about carrying out a disciplinary or grievance investigation.

What is a Disciplinary or Grievance Investigation?

A disciplinary investigation is a method for finding out all you reasonably can about a potential disciplinary or grievance issue in the workplace. The investigation allows you to:

  • explain to your employee what the potential problems are;
  • establish if there is an issue to deal with;
  • ensure you treat everyone fairly;
  • obtain evidence from all parties; and 
  • decide what action to take next. 

The disciplinary or grievance investigation should take place before the disciplinary hearing. You must carry out a reasonable disciplinary investigation.

Failure to do so may result in your business facing legal action. This is because any decisions you make as part of your disciplinary and grievance procedures will likely be unfair if you do not precede them with an investigation.

Steps to Take for Carrying Out an Investigation

When you face a disciplinary or grievance investigation, it is helpful to break it down into steps. You must provide a fair and thorough investigation as part of your requirement to pursue fair and full disciplinary and grievance procedures.

Deciding Who Should Investigate

The person carrying out your disciplinary or grievance investigation should investigate if there is a potential issue. Their job is not to determine if the employee is guilty. Therefore, it is essential that the person you choose:

  • is fair and objective;
  • adheres to your workplace policies and guidance;
  • collects a reasonable amount of information;
  • has training on how to carry out a disciplinary investigation;
  • gathers evidence from both sides; and 
  • respects confidentiality.

The person you choose could be your employee’s direct manager, but not if they are the one who has made a complaint or is a witness. They should also not be implicated in any way. Furthermore, they cannot be the same person holding the disciplinary hearing. Where the issue is complex, you may consider asking someone from outside your business to carry it out. 

Is Suspension Necessary?

Suspension should be a last resort, not a default response. Before suspending an employee, you must actively consider and document reasonable alternatives, such as temporary redeployment, remote working, adjusted duties, or restricting contact with specific colleagues or customers.

You should only suspend where none of these alternatives is workable with the employee present at work. Suspension may also be warranted where the case involves potential gross misconduct.

For example, because you cannot conduct the investigation with integrity, or cannot keep staff or the business safe.

If you suspend, it must be on full pay unless the contract expressly allows otherwise. You must be able to show that suspension was necessary and that you considered alternatives first, as otherwise you risk breaching the implied term of trust and confidence.

Any suspension should be kept as short as possible, reviewed regularly, and the employee should return to work as soon as the review shows suspension is no longer needed.

Considering the Length of Investigation

Investigating a potential disciplinary or grievance issue as soon as possible is essential. However, your investigation does need to be fair and thorough. Different scenarios will dictate extra time for completing an inquiry, as some may be more complex than others.

It may be helpful to detail in your discipline and grievance procedure some guidance on the time length for disciplinary and grievance investigations. If you do not, it will be for you as the employer or the person investigating the matter to decide on the length of it. It is important to communicate this with the employees involved. You may find during the investigation that you require more time. However, you should note that where investigations are delayed, the investigation report should explain why.

“The investigator’s job is to establish the facts, not to decide guilt, and the person who investigates should never chair the hearing. Employers who blur those two roles hand the employee an easy fairness argument. Give the roles to two different people from the start.”

Roxana Makhloughi
Roxana Makhloughi Trainee Solicitor, LegalVision

Gathering Evidence

You must be sure to gather reasonable evidence as part of your investigation. You may consider your time limits for gathering it and any information you have pinpointed in an investigation plan. When gathering evidence, you must keep written records of how and why you obtain it, including where specific evidence may be missing. When considering the evidence, you must abide by the law regarding data protection and your employee’s privacy rights. 

You may wish to gather:

  • emails;
  • paperwork;
  • phone records;
  • computer records;
  • witness statements; and
  • attendance records.

You should hold an investigation meeting to obtain witness evidence when the evidence is from an employee and the information is not straightforward. If you do, you should take notes and ensure the witness signs confirming they are correct. When holding a grievance meeting, ensure you comply with any rules regarding allowing a companion to be present. For disciplinary meetings, this only applies to those meetings that will result in disciplinary action. Therefore, for the disciplinary investigation meeting, your employee has no right to be accompanied. However, it is good practice to allow them to be.

Employees increasingly submit a data subject access request under UK GDPR once an investigation begins, often to obtain copies of the evidence gathered against them. You should be prepared to respond to any such request within the standard one month statutory timeframe. This obligation runs independently of, and does not pause the investigation itself. 

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Sexual Harassment Grievances and the Preventative Duty

Where a grievance investigation concerns an allegation of sexual harassment, you should also consider whether your business has met its duty under the Worker Protection (Amendment of Equality Act 2010) Act 2023 to take reasonable steps to prevent sexual harassment of employees, including harassment by third parties such as clients, contractors or customers. This duty has applied since 26 October 2024.

The duty applies regardless of the outcome of the specific complaint being investigated. If a tribunal later finds that sexual harassment occurred and that you failed to take reasonable preventative steps, it can uplift any compensation awarded by up to 25%. The Equality and Human Rights Commission also has separate powers to take enforcement action against employers who breach the duty.

As part of your investigation, you should record what preventative measures were in place at the time of the alleged incident. For example, your anti harassment policy, staff training, and reporting channels, as this evidence may be relevant beyond the immediate grievance outcome.

If the grievance concerns a report of sexual harassment, be aware that the report itself may be capable of amounting to a protected disclosure under whistleblowing law. Where that is the case, any dismissal or detriment connected to the employee having made the report can be automatically unfair, with no compensation cap and no minimum qualifying service required. You should flag this possibility to whoever is running the investigation so it is handled with the appropriate care.

Making a Decision

At the end of your disciplinary or grievance investigation, you will need to decide whether or not the allegations occurred. To continue a disciplinary or grievance procedure, you must be reasonably satisfied that they did, as this is based on the balance of probabilities.

Compile an Investigation Report

When you are carrying out a disciplinary investigation, you should ideally make a report with all that you have found. This should be shared with your employee.

Make Recommendations

You may have asked someone else to conduct the disciplinary investigation for you. In this case, they might recommend the next action to take.

What Could Be the Decision Resulting From a Disciplinary Investigation?

A disciplinary investigation may result in no action needed by the employer or employee. However, some action will likely need to be taken on most occasions. This could include:

  • informal action such as training or mediation;
  • further investigation;
  • amending internal disciplinary procedures; or
  • continuing with a full disciplinary hearing.
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Key Takeaways

As an employer faced with an employee who is not abiding by workplace rules, you should conduct a disciplinary investigation to decide your next course of action. Although there is no legal procedure for this, you should follow this article’s guidance to ensure that you carry it out fairly and thoroughly. This will also help you to avoid any repercussions at a later stage. In addition, carrying out a disciplinary investigation will guide you in your next steps, including whether a formal disciplinary hearing is required.

Please note that from January 2027, the two-year qualifying period for unfair dismissal claims will change to six months under the Employment Rights Act 2025. Therefore, employers should take caution and ensure investigations into short-service employees are carried out with the same rigour as for longer-serving staff, ahead of this change taking effect.

If you need help understanding how to conduct a disciplinary investigation, LegalVision provides ongoing legal support for all businesses through our fixed-fee legal membership. Our experienced employment lawyers help businesses manage contracts, employment law, disputes, intellectual property, and more, with unlimited access to specialist lawyers for a fixed monthly fee. To learn more about LegalVision’s legal membership, call 0808 196 8584 or visit our membership page.

Frequently Asked Questions

Is a disciplinary investigation the same as a disciplinary hearing?

No, a disciplinary investigation is the first stage you should take before deciding whether to carry out a disciplinary hearing. It allows you to gather evidence about what has allegedly taken place to guide you on your next course of action.

Are there rules on how to conduct a disciplinary investigation?

No statute sets the procedure. The Acas Code of Practice sets the standard, and tribunals take it into account when they assess fairness. An unreasonable failure to follow the Code lets a tribunal increase compensation by up to 25 per cent.

Can my employee bring a companion to the investigation meeting?

No. The statutory right to be accompanied applies to a grievance hearing and to a disciplinary hearing that could result in a formal warning or other disciplinary action. It does not apply to an investigation meeting. Your own policy or a contract may still give that right.

What standard of proof applies to a disciplinary investigation?

The balance of probabilities, not the criminal standard. You need a genuine belief on reasonable grounds that the employee committed the misconduct. You do not need to prove it beyond reasonable doubt, even where the allegation would also amount to a criminal offence.

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Roxana Makhloughi

Trainee Solicitor | View profile

Roxana is a Trainee Solicitor at LegalVision, bringing valuable in-house experience and a strong academic background to her role.

Qualifications:  Bachelor of Laws (Hons), Master of Laws, Graduate Diploma of Legal Practice, University of Essex.

Read all articles by Roxana

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