Employee Grievance Procedure: ACAS-Compliant UK Guide

Every UK employer needs a clear, written grievance procedure. When an employee raises a concern about their working conditions, management, pay, or treatment, how you respond can either resolve the issue quickly or escalate it into a costly employment tribunal claim. The ACAS Code of Practice on Disciplinary and Grievance Procedures sets the standard that tribunals use to assess whether your handling of a grievance was reasonable.

This guide explains how to set up and run a grievance procedure that is legally compliant, fair to all parties, and practical for small and medium-sized businesses.

What is a grievance and why does it matter

A grievance is a formal complaint raised by an employee about any aspect of their employment. Grievances can cover a wide range of issues, including terms and conditions of employment, working relationships with colleagues or managers, bullying and harassment, health and safety concerns, discrimination, changes to working practices, and pay or benefits disputes.

Handling grievances properly matters for three reasons. First, the ACAS Code of Practice requires employers to have a written grievance procedure and to follow it when a grievance is raised. Second, if a grievance is mishandled and the employee brings a tribunal claim, the tribunal can increase compensation by up to 25% for an unreasonable failure to follow the Code. Third, unresolved grievances damage morale, productivity, and staff retention — addressing them promptly is simply good management.

The ACAS Code: core principles for grievances

The ACAS Code establishes the following principles for handling grievances:

1. Employees should raise grievances formally in writing with their employer
2. Employers should arrange a meeting to discuss the grievance without unreasonable delay
3. The employee must be allowed to be accompanied at any formal grievance meeting
4. The employer should investigate the grievance and respond in writing
5. The employee must be given a right of appeal if they are not satisfied with the outcome

These steps form the minimum framework. Many employers build a more detailed procedure around them, but you must not fall below this baseline.

Informal resolution: the first step

Not every workplace complaint needs to go through a formal procedure. In many cases, an informal conversation between the employee and their line manager can resolve the issue quickly and without the stress of a formal process.

Encourage employees to raise concerns informally first. This might involve a private meeting with their manager, a facilitated conversation between colleagues, or a simple change to working arrangements.

However, there are situations where informal resolution is not appropriate. If the complaint involves serious allegations of harassment, discrimination, or whistleblowing, it should be dealt with formally from the start. Similarly, if the employee specifically requests a formal process, you should respect that choice.

Stage 1: Receiving the formal grievance

When an employee submits a formal grievance, they should do so in writing. The written grievance should set out the nature of the complaint, any relevant dates and details, the names of anyone involved, the outcome the employee is seeking, and any steps already taken to resolve the issue informally.

Acknowledge receipt of the grievance in writing as soon as possible — ideally within 2 working days. Explain the next steps and the expected timeframe for the process.

Who should handle the grievance

The person investigating and hearing the grievance should be someone who is not the subject of the complaint, is sufficiently senior to make decisions and implement outcomes, and is as impartial as possible.

In small businesses where management options are limited, consider using an external HR consultant or an alternative senior person. If the grievance is about the employee's direct manager, ensure the hearing is conducted by someone more senior or in a different reporting line.

Stage 2: Investigation

Before holding a grievance meeting, carry out a proportionate investigation into the matters raised. The depth of investigation will depend on the nature and complexity of the grievance.

An investigation may involve interviewing the employee who raised the grievance, interviewing witnesses, reviewing relevant documents such as emails, rotas, or policies, examining CCTV footage or other records, and obtaining specialist advice where appropriate.

Dealing with the subject of the grievance

If the grievance is about another employee's behaviour, that person must be informed and given a fair opportunity to respond to the allegations. Natural justice requires that they know the case against them and can put forward their side. This can be a delicate balancing act between the complainant's right to raise concerns and the subject's right to fair treatment.

Stage 3: The grievance meeting

Arrange a formal grievance meeting with the employee without unreasonable delay. Give them reasonable notice — at least 5 working days is good practice.

Right to be accompanied

Under Section 10 of the Employment Relations Act 1999, the employee has a statutory right to be accompanied at a formal grievance meeting by a trade union representative or a fellow worker. The companion can address the hearing and confer with the employee but cannot answer questions on the employee's behalf.

If the employee's chosen companion is unavailable on the proposed date, you must postpone the meeting to an alternative date suggested by the employee, provided it is within 5 working days of the original date.

Running the meeting

Structure the meeting as follows:

1. Introduce the purpose of the meeting and confirm the process
2. Ask the employee to explain their grievance in their own words
3. Ask questions to clarify the issues and gather further information
4. Allow the companion to make representations if they wish
5. Summarise the key points to ensure you have understood correctly
6. Adjourn to consider the grievance and the evidence gathered

Stage 4: The grievance outcome

After the meeting and any further investigation, write to the employee setting out your decision. The outcome letter should include a summary of the grievance, the findings of your investigation, your decision and the reasons for it, any actions you will take to resolve the grievance, and the employee's right to appeal.

Possible outcomes

The range of outcomes will depend on the nature of the grievance but could include upholding the grievance in full and implementing the requested changes, partially upholding the grievance with modified actions, not upholding the grievance with clear reasons, mediation between the parties, changes to policies or procedures, disciplinary action against another employee if their behaviour warrants it, or changes to working arrangements or reporting lines.

Stage 5: The appeal

If the employee is not satisfied with the outcome, they must be given the right to appeal. The appeal should be heard by a more senior manager who was not involved in the original decision, wherever possible.

The employee should set out their grounds of appeal in writing. Common grounds include that the investigation was inadequate, that relevant evidence was overlooked, that the decision was unreasonable on the facts, or that the process was procedurally unfair.

The appeal hearing follows a similar format to the original meeting. The appeal manager can uphold the original decision, overturn it, or substitute a different outcome. Communicate the appeal decision in writing. The appeal decision is final.

Grievances raised during disciplinary proceedings

This is a common tactical issue. If an employee raises a grievance during an ongoing disciplinary process, consider whether the grievance is related to the disciplinary matter. If it is — for example, the employee alleges that the disciplinary action is motivated by discrimination — you may need to pause the disciplinary and deal with the grievance first. If the grievance is unrelated, both processes can generally run in parallel.

Constructive dismissal risk

If you fail to address a legitimate grievance — or if you handle it so badly that the employee loses trust and confidence in you as an employer — the employee may resign and claim constructive dismissal. The implied term of mutual trust and confidence is at the heart of every employment contract, and ignoring or mishandling a grievance can amount to a fundamental breach.

This is one of the strongest reasons to take every grievance seriously, investigate properly, and follow the ACAS Code. Even if you ultimately do not uphold the grievance, the process of listening and investigating demonstrates that you have taken it seriously.

Record keeping and GDPR

Maintain comprehensive records of every stage of the grievance process. Keep the written grievance, investigation notes and evidence, meeting notes, outcome and appeal letters, and any related correspondence.

Retain these records for the duration of employment plus at least 6 years. Handle all records in accordance with UK GDPR requirements — inform the employee about what data you are processing and why, and ensure that access is limited to those with a legitimate need.

Frequently asked questions

Next steps

Key takeaways

A fair grievance procedure follows a clear path: receive the complaint in writing, investigate thoroughly, hold a meeting where the employee can explain their concerns, make a reasoned decision, and offer an appeal. Follow the ACAS Code at every stage, maintain confidentiality, and document everything. Handling grievances well is not just about avoiding tribunal claims — it builds trust and shows your workforce that their concerns are taken seriously.

If grievance outcomes require changes to pay, working hours, or benefits, ensure these are reflected accurately in your payroll. Use our Payroll Tax Calculator to check the impact of any changes on take-home pay and deductions.