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Formal Grievance Procedure: ACAS Code Guide

You have a workplace complaint. Follow the ACAS Code of Practice to raise a formal grievance. Learn the steps, deadlines, and how to prepare for tribunal if needed.

Quick Answer: Submit written grievance to your manager or HR. Employer must acknowledge within 2 working days. Formal hearing within 5-10 working days. Appeal within 5 working days of outcome. If employer fails to follow ACAS Code, tribunal can increase compensation by 25%. Must complete grievance before tribunal claim (except constructive dismissal).

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ACAS Code of Practice Steps

  1. Written grievance: Submit in writing to manager or HR. Detail the complaint, dates, witnesses, what you want (apology, reversal, compensation).
  2. Acknowledgment: Employer must acknowledge within 2 working days.
  3. Formal hearing: Employer holds hearing within 5-10 working days. You can bring a companion (friend, union rep).
  4. Outcome: Employer gives decision in writing within 5-10 working days.
  5. Appeal: You can appeal within 5 working days if outcome is unfair.

What to Include in Your Grievance Letter

Date of the issue, what happened (specific incident or pattern), who was involved, impact on you, what you want (resolution), dates and witnesses. Keep it factual, professional, not emotional.

Failure to Follow ACAS Code

If employer ignores the code (no hearing, no appeal, rushed process), tribunal can increase compensation by 25%. This is powerful leverage - mention it to your employer.

Reviewed by Sarah Wood  ·  Founder, Fightingback. 12 years designing legal-tech and consumer-rights products at Creative Sauce London.

Not a solicitor. Guides are grounded in current UK statute, ombudsman rules and reported case law. Last reviewed: 6 July 2026.

How to Raise a Formal Grievance at Work (ACAS Code) | FightingBack

How to Raise a Formal Grievance at Work

A complete guide to the ACAS Code of Practice: what to put in your grievance letter, the timescales your employer must meet, your right to be accompanied at the hearing, and how a badly-handled grievance can add 25% to a later tribunal award.

Quick Answer: Put your grievance in writing to your manager or HR. Under the ACAS Code of Practice 2015, the employer must acknowledge it promptly, hold a formal hearing (usually within 5-10 working days) at which you can bring a colleague or trade union representative, and give you a written outcome. You can appeal in writing, normally within 5 working days. If the employer ignores the Code, an employment tribunal can raise your compensation by up to 25%. You must complete a grievance before starting most tribunal claims.

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What a Grievance Actually Is

A grievance is any concern, problem or complaint you raise formally with your employer. Common grievances include bullying or harassment, being paid less than the National Minimum Wage or below the amount in your contract, unlawful deductions from wages, refused holiday pay, discrimination on grounds protected by the Equality Act 2010, unsafe working conditions, being passed over for promotion for an unlawful reason, or being denied a flexible working request without proper procedure.

The right to raise a grievance is not a right you can be dismissed for using. Detriment or dismissal because you raised a genuine grievance can itself amount to unfair dismissal under the Employment Rights Act 1996 or victimisation under the Equality Act 2010, and in some cases to a whistleblowing claim under the Public Interest Disclosure Act 1998.

Try Informal Resolution First

The ACAS Code of Practice on Disciplinary and Grievance Procedures 2015 is clear that most workplace issues are best sorted informally, in a one-to-one conversation with a manager or HR, before anyone reaches for a formal process. Where the issue is safe to raise informally and you feel able to, do that first and make a written note of what was said and agreed. If it does not fix the problem, or if the problem is too serious for an informal chat, move to the formal process.

The exception is where the underlying conduct is so serious (a serious health and safety concern, sexual harassment, discrimination, or fraud) that going formal straight away is reasonable. In those cases raise it in writing without delay.

The Formal Grievance Process, Step by Step

  1. Put it in writing. Address a formal letter or email to your manager, or to HR if the manager is the subject of the grievance. Label it clearly as a formal grievance. Set out the facts, dates, witnesses and impact, and say what outcome you are asking for.
  2. Acknowledgement. The ACAS Code expects the employer to respond "without unreasonable delay." In practice a written acknowledgement should arrive within two working days confirming what happens next.
  3. Formal hearing. The employer must hold a meeting to discuss the grievance, usually within 5 to 10 working days. Under section 10 of the Trade Union and Labour Relations (Consolidation) Act 1992 you have a statutory right to be accompanied by a colleague or an ACAS-certified trade union representative at that meeting.
  4. Written outcome. After the hearing the employer gives you a written decision explaining what has been decided and why, ordinarily within 5 to 10 working days.
  5. Appeal. You can appeal in writing, usually within 5 working days of the outcome. Say what you disagree with and why. The appeal should be heard by a different, more senior manager where possible.
  6. ACAS Early Conciliation. If it does not resolve and you may want to bring a tribunal claim, contact ACAS to start Early Conciliation. In most cases this must be done within three months less one day of the event you are complaining about.

What to Put in the Grievance Letter

A good grievance letter is calm, factual and specific. Vent to a friend, not on the page. The letter should include:

Example Opening for a Grievance Letter

Formal Grievance

Dear [Name of manager / HR contact],

I am writing to raise a formal grievance under the ACAS Code of Practice on Disciplinary and Grievance Procedures 2015. I set out below the facts, why I say the conduct complained of breaches [my contract of employment / the company's bullying policy / the Equality Act 2010], the impact on me, and the outcome I am asking for.

[Facts, in date order, with names, dates, and any supporting documents referenced or attached.]

I request a formal grievance hearing at the earliest reasonable opportunity. I intend to be accompanied at that hearing by a colleague or trade union representative under section 10 of the Trade Union and Labour Relations (Consolidation) Act 1992.

Yours sincerely,
[Your name]

Timescales the Employer Has to Meet

The ACAS Code does not set precise minimum or maximum periods, and the words used are "without unreasonable delay." That flexibility is a feature, not a bug: tribunals judge each case on its facts. In practice, the widely-accepted timings are:

If your employer misses these by a long way with no good reason, that is a Code breach and evidence a tribunal can take into account.

The Right to Be Accompanied

Section 10 of the Trade Union and Labour Relations (Consolidation) Act 1992 gives every worker (not just an "employee") a legal right to be accompanied at any formal grievance or disciplinary hearing by either a fellow worker or a trade union representative certified in writing by their union as competent to do the role. The employer cannot refuse a lawful choice of companion, and cannot punish you for exercising the right.

The companion can address the hearing, put and sum up your case, and confer with you during the meeting. They cannot answer questions on your behalf, but their presence often changes the tone.

What Happens If the Employer Ignores the ACAS Code

Under section 207A of the Trade Union and Labour Relations (Consolidation) Act 1992, an employment tribunal has the power to increase or decrease compensation by up to 25% if either side has unreasonably failed to follow the ACAS Code.

In practice that means:

Practical tip: If the employer starts cutting corners, put it in writing at the time. A short email that says "For the record, I asked to be accompanied under section 10 TULRCA 1992 and this was refused" is powerful evidence months later.

Do You Have to Raise a Grievance Before a Tribunal?

For almost every tribunal claim (unfair dismissal, discrimination, unlawful deduction from wages, whistleblowing detriment, breach of contract), yes. The tribunal will expect to see that you gave the employer a fair chance to fix the problem first. The one clear exception is constructive dismissal: because you are treating yourself as having been dismissed, you can bring a claim without exhausting the internal process, though you should still normally raise a grievance if it is safe and possible.

Before starting a claim you also have to notify ACAS to begin Early Conciliation. That must ordinarily happen within three months less one day of the event you are complaining about. Miss that deadline and you usually lose the right to bring the claim.

Common Situations

Bullying, harassment or discrimination

If the treatment is based on a protected characteristic under the Equality Act 2010 (age, disability, gender reassignment, marriage/civil partnership, pregnancy/maternity, race, religion or belief, sex, sexual orientation), a grievance is often the first step towards a discrimination claim. Keep contemporaneous notes: dates, exact words used, witnesses.

Unpaid or underpaid wages

Deductions from wages that are not authorised by contract, statute, or your prior written consent are unlawful under Part II of the Employment Rights Act 1996. A grievance letter that quotes the specific missing amount, the pay reference period, and the section of the Act tends to be answered fast.

Refused holiday pay or missing rest breaks

Rights to paid annual leave and to rest breaks are set by the Working Time Regulations 1998. Failure to allow leave or pay it correctly can be raised as a grievance and, if unresolved, taken to a tribunal.

Health and safety concerns

You have a right, under section 44 of the Employment Rights Act 1996, not to be subjected to a detriment for raising reasonable health and safety concerns. A written grievance creates the paper trail that protects that right.

Frequently Asked Questions

Can I raise a grievance anonymously?

Rarely helpful. The employer has to be able to investigate what you have said, put it to any accused colleague, and give you a hearing. An anonymous complaint can be looked at as a general concern but cannot really run through the ACAS Code.

What if the person I want to complain about is my manager?

Send the grievance to their manager, or to HR, and say clearly that a conflict of interest means you cannot send it to your own line manager. Ask that the hearing be chaired by someone unconnected to the complaint.

What if I am still in my probation period?

The ACAS Code still applies. Some statutory rights (such as ordinary unfair dismissal) need 2 years' service, but grievance rights, discrimination rights, unlawful deductions and health-and-safety detriment protection all apply from day one.

Can I record the hearing?

Not without agreement. If the employer refuses to allow a recording, ask for written minutes and request a copy for approval afterwards.

How long do I have to bring a tribunal claim?

Usually three months less one day from the last act complained of. That clock is paused while ACAS Early Conciliation is running. Missing this deadline is the single biggest reason perfectly good claims fail.

Ready to Raise Your Grievance?

Fightingback's Work Rights tool asks you a short set of questions and drafts a formal ACAS-Code-compliant grievance letter you can send to your employer today. Your first letter is free, no signup needed.

Draft my grievance letter