Received a disciplinary outcome you disagree with? Learn how to appeal, what grounds to use, and how to prepare. Free expert guide from National Employees Union.
A disciplinary outcome can feel final. A written warning goes on your record. A dismissal ends your income. But every formal disciplinary process must include a right of appeal — and that appeal is not a formality. It is a genuine opportunity to overturn or reduce the outcome. This guide explains when you can appeal, what grounds carry weight, and how to build a case that gives you the strongest chance of success.
Contents
- What is a disciplinary appeal?
- Your right to appeal
- Grounds for appeal
- How to write an appeal letter
- What happens at an appeal hearing
- Possible outcomes
- What if the appeal fails?
- FAQs
- How National Employees Union can help
What is a disciplinary appeal?
A disciplinary appeal is a formal review of a decision made against you at a disciplinary hearing. The review should be conducted by someone senior to the original decision-maker — someone who played no part in the investigation or the hearing itself.
The appeal exists to catch errors. Those errors might relate to the facts, the procedure, or the proportionality of the sanction. Without an appeal stage, mistakes in the original process would stand unchallenged. That is why the ACAS Code of Practice requires every employer to offer one.
An appeal follows the hearing, and our complete guide to disciplinary and grievance procedures shows where it sits in the process.
Your right to appeal
The right to appeal is established in the ACAS Code and reinforced by case law. Your employer must confirm this right in the outcome letter. That letter should include the decision, the reasons behind it, the sanction imposed, and instructions for how to appeal — including the deadline.
Most employers set a deadline of five working days from receipt of the outcome letter. Some allow longer. Check your employer’s disciplinary policy for the exact timeframe. If the letter does not mention your right to appeal, raise this in writing immediately — the omission is itself a procedural failing.
Missing the deadline can extinguish the right. If you need more time, request an extension in writing before the deadline passes. Put the request on record. A reasonable employer will grant it.
Grounds for appeal
An appeal is not a chance to restate your case in stronger terms. It must be built on specific grounds — reasons why the original decision was wrong. Tribunals and appeal panels look for three categories.
A flawed investigation is the most common ground, so compare yours with what a proper investigation meeting looks like.
The process was flawed
Your employer failed to follow a fair disciplinary and grievance procedure. Examples include not sharing the evidence before the hearing, not allowing you to bring a companion, introducing allegations that were not in the original invitation letter, reaching the decision before hearing your response, or having the same manager investigate and chair the hearing.
Procedural failures matter because they undermine the fairness of the outcome. An employer cannot argue the decision was sound if the process that produced it was broken.
The decision was wrong on the facts
New evidence has come to light that was not available at the hearing. A witness has changed their account. The evidence your employer relied on does not support the finding. The investigation missed a relevant piece of information.
Factual errors go to the heart of the decision. If the facts do not support the allegation, the outcome built on those facts cannot stand.
The sanction was disproportionate
The allegation may have been proven, but the sanction went too far. A first offence that does not amount to gross misconduct should not normally result in dismissal. A verbal warning for a minor issue should not escalate to a final written warning. The sanction should reflect the seriousness of the conduct, your disciplinary record, your length of service, and how similar cases have been handled.
Inconsistency is a strong ground. If a colleague committed the same act and received a lesser sanction, that disparity supports a disproportionality argument.
How to write an appeal letter
The appeal letter is the foundation of your case. It should be clear, factual, and structured around specific grounds.
Structure
- State that you are appealing. Reference the outcome letter, the date you received it, and the decision you are challenging.
- Set out your grounds. Number each ground separately. Under each one, explain what went wrong, cite the evidence that supports your position, and state how the error affected the outcome.
- State the remedy you seek. Do you want the decision overturned? The sanction reduced? A rehearing with a different panel? Be specific.
- Request disclosure. Ask for copies of any documents the original panel relied on, plus the notes from the hearing. You are entitled to these.
Tone
Write in the same register you would use in a formal letter to a senior manager. Do not use emotional language. Do not accuse the decision-maker of bias unless you have evidence of it. Let the facts carry the argument — they are harder to dismiss than assertions.
Example opening
> I am writing to appeal the decision communicated in your letter dated [date], in which I received a [sanction]. I received the outcome letter on [date] and submit this appeal within the required timeframe. My grounds are set out below.
What happens at an appeal hearing
The appeal hearing is a formal meeting. A more senior manager — one not involved in the original process — should chair it. You have the right to be accompanied by a trade union representative or colleague, just as you did at the original hearing.
You keep your right to be accompanied at the appeal, exactly as you had it at the first hearing.
The format
The panel will review the original decision in light of your appeal grounds. Depending on the employer’s policy, the appeal may take one of two forms:
- A review — the panel examines the paperwork, your appeal letter, and the original hearing notes, then decides whether the outcome was fair
- A rehearing — the case is heard again from the start, with all evidence presented afresh
A rehearing gives you more scope to present your case. If your employer offers only a review but your grounds include new evidence or serious procedural failings, push for a rehearing. Put the request in writing and explain why a paper review would be insufficient.
What to do at the hearing
Present your grounds in order. Refer to specific documents and evidence. If a procedural step was missed, point to the relevant paragraph of the ACAS Code. If you have new evidence, present it and explain why it was not available at the original hearing. If the sanction was disproportionate, present the comparators — how similar cases were treated.
Your companion can present your case, ask questions, and confer with you privately during the hearing. Use them. A trained trade union representative will know which procedural points carry weight and how to frame the proportionality argument.
Possible outcomes
The appeal panel can:
- Uphold the original decision — the outcome stands
- Overturn the decision — the allegation is not proven, or the process was so flawed that the outcome cannot stand
- Reduce the sanction — the allegation stands but the original sanction was out of proportion (for example, a dismissal reduced to a final written warning)
- Order a rehearing — the process was flawed and the case should be heard again by a different panel
The panel’s decision should be confirmed in writing, with reasons.
If the outcome leaves a warning on your record, check how long a written warning lasts.
What if the appeal fails?
A failed appeal is not the end. If you were dismissed and believe the dismissal was unfair — because the process was flawed, the reason was not genuine, or the sanction was disproportionate — you may have a claim for unfair dismissal.
The critical deadline is three months minus one day from the date of your dismissal to begin ACAS Early Conciliation. This deadline runs from the original dismissal date, not the appeal outcome date.
If you received a warning rather than dismissal, the appeal outcome is usually final within the internal process. But the warning should have an expiry date (typically 6 or 12 months). If your employer relies on an expired warning in a future disciplinary, challenge that reliance.
If the appeal fails and you were dismissed, the next question is whether the dismissal was unfair.
A claim runs to a strict timetable, which our step-by-step guide to the Employment Tribunal sets out.
FAQs
Do I have to appeal before I can go to an Employment Tribunal?
You are not legally required to appeal first. But Employment Tribunals expect you to have used internal processes. If you did not appeal and the tribunal considers you should have, it can reduce your compensation by up to 25% for failure to follow the ACAS Code of Practice. Appeal first unless there is a compelling reason not to.
Can the appeal make the outcome worse?
In most cases, no — the appeal should not result in a harsher sanction than the original decision. However, some employer policies do allow the appeal panel to increase the sanction. Check your employer’s disciplinary policy before you appeal. Even where the policy allows it, increasing a sanction on appeal is rare and carries significant legal risk for the employer.
Can I submit new evidence at the appeal?
Yes. If you have evidence that was not available at the original hearing — a witness statement, a document you have since obtained, or information that has come to light — present it at the appeal. Explain why it was not available before. New evidence that undermines the original finding is one of the strongest grounds for overturning a decision.
How long should the appeal take?
Your employer should hear the appeal without unreasonable delay — typically within two to four weeks of receiving your appeal letter. If weeks pass without a date being set, chase in writing. Unreasonable delay can itself be challenged as a procedural failing.
Can I appeal a verbal warning?
Yes. The right to appeal applies to all formal outcomes — verbal warnings, written warnings, final written warnings, and dismissal. A verbal warning is still a formal sanction that goes on your record. If it is unjustified, appeal it.
How National Employees Union can help
An appeal is your last chance within the internal process to correct a wrong outcome. The right support at this stage can change the result.
National Employees Union members get:
- Review of the original decision — we assess whether the process was fair, the facts were established, and the sanction was proportionate
- Help drafting the appeal letter — structured around the grounds most likely to succeed
- A trained representative at the appeal hearing — someone who knows what procedural arguments carry weight and how to present them
- Advice on next steps if the appeal fails — including whether you have grounds for an unfair dismissal claim or Employment Tribunal application
- Time limit monitoring — we track the three-month deadline so you do not miss it
You do not need to navigate this alone. Members get expert representation at every stage of the process.
Join the National Employees Union
Membership from £15/month.
Written by the National Employees Union team. We represent employees in disciplinary appeals across the UK every day. This guide is reviewed regularly and was last updated in July 2026. For advice on your specific situation, contact us.
