The ACAS grievance procedure, step by step

The ACAS Code of Practice on Disciplinary and Grievance Procedures applies equally to grievances as to disciplinary matters. Failure to follow it allows employment tribunals to adjust any compensation award by up to 25%.

Step 1: Informal resolution

Encourage informal resolution where possible. A direct conversation between the employee and their line manager (or HR) often resolves the issue without escalation. The Code expects employers to attempt informal resolution before formal procedures, where appropriate.

Some grievances — especially those alleging serious misconduct, harassment, or discrimination — should go straight to a formal process.

Step 2: Written grievance

The employee submits the grievance in writing. The grievance should set out:

• What the complaint is.
• When it happened.
• Who was involved.
• What outcome the employee is seeking.

There is no statutory form for a grievance — even an email can be a formal grievance if it is clear that the employee is raising one.

Step 3: Invitation to a hearing

Write to the employee inviting them to a grievance hearing. The letter should:

• Confirm the date, time and location.
• Confirm the right to be accompanied by a trade union representative or work colleague.
• Provide reasonable notice (typically at least 5 working days).
• Indicate who will conduct the hearing.

Step 4: The grievance hearing

• Conducted by an impartial manager, ideally not directly involved in the matters complained of.
• The employee presents their grievance.
• Take notes and consider what additional evidence (witnesses, documents) is needed.
• The hearing is not adversarial — the aim is to understand the complaint.
• Adjourn before reaching a decision.

Step 5: Decision and outcome letter

Write to the employee with:

• The outcome — upheld, partially upheld, or not upheld.
• The findings for each element of the grievance.
• Any actions the employer will take.
• The right of appeal, including the timescale and who to appeal to.

Step 6: Appeal

Always offer a right of appeal. The appeal should be heard by:

• A more senior manager than the one who took the original decision.
• Someone not previously involved in the matter.

The appeal should consider whether the original procedure was fair and whether the outcome was reasonable.

Concurrent disciplinary and grievance

Where an employee raises a grievance during a disciplinary process, the employer should consider:

• Pausing the disciplinary to deal with the grievance first, especially if the grievance relates directly to the disciplinary.
• Running them in parallel if the grievance is unrelated.
• Keeping the two processes separate in terms of decision-makers and documentation.

Common procedural failings

• Failing to invite the employee to a hearing.
• Not allowing the right to be accompanied.
• The same manager investigating, hearing and deciding the appeal.
• No written outcome.
• No right of appeal offered.

ERA 2025 implications

From October 2026, employers will be liable for harassment by third parties (customers, clients, contractors) unless they have taken all reasonable steps to prevent it. Grievance procedures should explicitly cover third-party harassment, and employers should document the steps taken to prevent it.

Official source: ACAS Code of Practice on Disciplinary and Grievance Procedures.