Written Warning Guide for Employers

A written warning is a formal step an employer can take when addressing concerns about an employee’s conduct or performance.

Employers generally issue written warnings after informal measures have failed or where the situation is too serious to be dealt with informally but does not yet warrant dismissal. Common examples include repeated lateness, breaches of workplace rules or ongoing underperformance. It should act as a record that an issue has been raised and that the employee has been made aware of the consequences should the matter continue or worsen.

When issuing a written warning, employers must be able to demonstrate that the disciplinary process followed was reasonable and in line with the ACAS Code of Practice. Failure to do so may expose the business to legal risks, including claims for unfair dismissal or constructive dismissal if the matter escalates.

In this guide, we set out what employers need to know about written warnings and how to mitigate legal risk during the disciplinary process.

 

Section A: What is a Written Warning?

 

A written warning is a formal step in the disciplinary process used when an employer has concerns about an employee’s behaviour or performance that require more than an informal conversation. Under UK employment law, it forms part of the employer’s record-keeping in relation to managing conduct or capability issues and must be handled in accordance with the ACAS Code of Practice on Disciplinary and Grievance Procedures.

There is a clear distinction between informal and formal warnings. Informal warnings are typically given verbally, often as part of day-to-day management, and are used to address issues early. For example, a manager may speak with an employee about a one-off instance of lateness or a minor error in work. These conversations are not part of the formal disciplinary record but may be noted for future reference.

A formal written warning, on the other hand, follows a structured disciplinary process. It must be based on evidence, issued after an investigation and a disciplinary meeting, and clearly set out the issue, the expected improvement and the timeframe for change. The warning must also state what further action may be taken if there is no improvement.

 

1. Types of written warnings at work

 

There are two main types of formal warnings used in the workplace: a first written warning and a final written warning. A first written warning is usually issued when an employee’s conduct or performance falls below expectations but is not serious enough to warrant dismissal. If the issue continues or a more serious concern arises, a final written warning may be given, making it clear that further breaches could lead to dismissal. Informal warnings may also be used for minor issues, often through a verbal conversation. Each warning should follow a fair process and be properly documented.

An expired warning is a formal warning that has passed its active period and should no longer be used to influence future disciplinary decisions. Most warnings remain live on an employee’s record for a set period, such as six or twelve months. Once that period ends, the warning is considered spent. While employers may keep a record for internal purposes, expired warnings should not form the basis for further disciplinary action. Relying on an expired warning to justify dismissal or a harsher sanction could be challenged as unfair, especially if the employer has not followed their own disciplinary policy.

 

Table: Types of Warnings

 

Type of Warning	When It’s Used	Typical Duration
First Written Warning	For less serious misconduct or performance issues	6 to 12 months
Final Written Warning	When there has been no improvement or the issue is more serious	12 months or as specified
Expired Warning	No longer active, should not influence decisions unless part of a broader pattern	After warning period ends

 

 

2. Role of warnings in the workplace

 

Employers may issue written warnings in a wide range of circumstances; misconduct is a common reason, as are performance concerns. The purpose of a written warning is not simply to punish but to give the employee a fair opportunity to improve. It should be constructive, specific and time-bound. Employers must take care to apply the same standards to all staff, avoid assumptions and keep detailed records in case the matter later progresses or is challenged.

 

 

Section B: When Should a Written Warning Be Issued?

 

A written warning should be issued when an employee’s conduct or performance falls short of the standards expected and when informal steps have not resolved the issue, or the matter is too serious to be addressed informally. It is not meant for every minor concern but is appropriate where there is a clear breach of policy, failure to meet agreed expectations or a repeat of previous concerns.

Examples of when a written warning may be justified include persistent lateness, failure to follow reasonable instructions, breaches of health and safety procedures or ongoing underperformance despite earlier support. Employers may also issue a written warning after a single, more serious incident that does not meet the threshold for a final warning or dismissal, such as inappropriate conduct in the workplace or unauthorised absence.

Before issuing a written warning, employers must carry out a fair process. This usually means conducting a proportionate investigation into the facts and then holding a disciplinary hearing where the employee has the opportunity to explain their side. Any evidence should be shared with the employee in advance, and they should be given reasonable notice of the hearing and the right to be accompanied. A written warning should not come as a surprise to the employee, and the hearing should provide a fair chance to respond.

The ACAS Code of Practice sets out the minimum standards that employers should follow in disciplinary situations. While not legally binding, the Code is taken into account by employment tribunals when assessing whether an employer acted fairly. Failure to follow the Code can result in an uplift in any compensation awarded to an employee, of up to 25 per cent. The Code encourages early resolution, fair treatment, and consistency. It also emphasises the importance of clear communication, proper documentation, and giving employees the opportunity to appeal.

Employers should ensure that their internal disciplinary procedures align with the ACAS Code and that any decision to issue a written warning is based on evidence, handled fairly, and properly recorded. Consistency is important to avoid claims of unfair treatment or discrimination, and managers involved in disciplinary matters should be trained to apply the correct procedure.

 

Section C: Legal Requirements when Issuing Written Warnings

 

A written warning is a serious matter for an employee, so employers are required to handle the process with care and in full compliance with their legal obligations. They also have to apply the rules consistently and ensure that the decision is based on evidence.

Failing to follow proper procedures can result in claims of unfair or constructive dismissal, particularly if the warning is later used to justify more serious action such as dismissal.

In practice, this means a written warning should ordinarily only follow a proper disciplinary process. Employers are expected to carry out a reasonable investigation to establish the facts. The employee should be told clearly what the allegation is and be given enough information to respond. The investigation must be impartial, and where possible, someone other than the person making the disciplinary decision should carry it out.

Once the investigation is complete, the employee should be invited to a disciplinary hearing. That invitation must be made in writing. The letter should explain the nature of the concern, outline the evidence gathered, and confirm the potential outcomes of the meeting. The employee must be given reasonable notice to prepare and should be told that they have the right to be accompanied.

 

Table: Disciplinary Process Checklist

 

Step	Description
Investigation	Gather facts and evidence before any decision is made
Written Notification	Inform the employee in writing of the allegations and the date of the hearing
Right to Be Accompanied	Employee may bring a colleague or trade union representative to the hearing
Disciplinary Hearing	Allow the employee to respond to the allegations before a decision is made
Written Outcome	Provide the decision in writing, including details of the warning and right to appeal
Appeal Process	Offer the employee a chance to challenge the decision in a fair and impartial hearing

 

Under the Employment Relations Act 1999, employees have a statutory right to be accompanied at a disciplinary meeting by a colleague, trade union representative or official employed by a trade union. Employers must inform the employee of this right in the hearing invitation. The companion can confer with the employee, present their case and sum up, but they cannot answer questions on their behalf.

The disciplinary hearing must be conducted fairly. The person chairing the meeting should keep an open mind and allow the employee to respond fully to the allegations. It is important to listen carefully, ask questions where necessary and consider any mitigating circumstances. If new evidence emerges during the hearing, it may be appropriate to pause the process and investigate further.

Once the hearing has concluded, the decision should be communicated to the employee in writing. If the outcome is a written warning, the letter should clearly explain the reason for the warning, the expected improvement and the timeframe for achieving it. The letter should also set out how long the warning will remain on file and what further action may follow if there is no improvement. Typically, a first written warning might remain live for six to twelve months, depending on the nature of the issue and the terms of the employer’s disciplinary policy.

The employee should also be informed of their right to appeal. The appeal must be heard by someone not involved in the original decision, ideally someone more senior. The appeal process must follow the same principles of fairness and transparency as the original hearing.

Employers must keep copies of all relevant documents, including the invitation to the hearing, meeting notes, the warning letter and any correspondence related to an appeal. These records provide important evidence if the process is later challenged and help ensure consistency across the organisation.

 

Section D: How Long Does a Written Warning Last?

 

The length of time that a written warning remains active will usually depend on the seriousness of the issue and the terms of the employer’s disciplinary policy. In most cases, a first written warning will remain on the employee’s record for a set period, typically between six and twelve months. The warning is considered “live” during this time, meaning it can be taken into account if there are further conduct or performance issues.

A first written warning is usually issued for less serious concerns, where the employer wants to set clear expectations and offer the employee an opportunity to improve. If there is no repeat of the behaviour or issue during the warning period, the warning will expire, and it should not be used in future disciplinary decisions. Employers may still keep a record of it internally, but it should not carry weight in any future proceedings once it has expired.

A final written warning is more serious. It may be given where there has been no improvement after a previous warning, or where the misconduct or poor performance is more severe but does not justify dismissal on its own. Final warnings typically remain live for twelve months, but employers may specify a longer or shorter period depending on the circumstances. Any decision to vary the length should be clearly explained and applied consistently.

Once a warning has expired, it should no longer influence disciplinary outcomes. However, there may be some limited circumstances where an employer refers to past warnings, for example where there is a pattern of repeated behaviour over a longer period. In such cases, employers must take care not to unfairly rely on expired warnings when making decisions that could lead to dismissal.

Employers should ensure that warning letters state how long the warning will remain active, when it will expire and what consequences may follow if the issue continues.

 

Section E: Written Warning Letter Template

 

A written warning letter is a formal document that confirms the outcome of a disciplinary hearing. It should set out the details of the concern, the findings of the meeting and the action the employer expects the employee to take. The letter must be clear, accurate and professional. It is important that it reflects what was discussed during the hearing and includes all relevant information so that the employee fully understands the implications.

Every written warning letter should contain certain key elements. These are not just best practice; they help demonstrate that the employer has acted fairly and transparently, which is important if the process is ever challenged. At a minimum, the letter should include:

 

• The date of the letter
• The reason for the warning, with enough detail to explain what the concern is and how it was established
• The date of the disciplinary hearing, who attended, and a brief summary of the discussion
• The standard of behaviour or performance expected going forward
• The timescale for improvement, if relevant
• How long the warning will remain live on the employee’s record
• Any support or follow-up action the employer will provide
• What will happen if there is no improvement or the issue happens again
• The employee’s right to appeal, including the timeframe and how to submit the appeal

 

Below is a sample written warning letter that employers in the UK can customise according to their needs:

 

[Your Company Letterhead]
[Date]

Private and Confidential

To: [Employee Name]
Job Title: [Employee’s job title]
Department: [Department name]

Subject: Written Warning – [Conduct/Performance Issue]

Dear [Employee’s name],

Following the disciplinary hearing held on [date], attended by yourself, [insert names of any managers or HR representatives present], I am writing to confirm the outcome of that meeting.

During the hearing, we discussed concerns regarding [brief summary of the issue, e.g. repeated lateness on specific dates, failure to meet agreed targets, or inappropriate behaviour]. After considering the evidence and your response, we have decided to issue you with a formal written warning under the company’s disciplinary procedure.

The reason for this warning is [explain the issue again briefly, including any relevant examples].

We expect you to [set out the required improvement, e.g. arrive on time for all scheduled shifts, meet specific performance targets]. This warning will remain active for [insert duration, e.g. six months] from the date of this letter. A copy will be kept on your personnel file for reference during this period.

Please be aware that further incidents or failure to improve could lead to more serious disciplinary action, which may include a final written warning or dismissal.

We will support you in meeting the expectations set out above. [Optional: insert details of any assistance, training, or follow-up reviews the company will provide.]

You have the right to appeal this decision. If you wish to appeal, you should do so in writing within [number] working days of receiving this letter. Your appeal should be sent to [name, job title, and contact details of the relevant person].

Yours sincerely,
[Manager’s name]
[Job title]
[Company name]

 

Employers should keep a signed copy of the letter on the employee’s personnel file. It is also advisable to ask the employee to acknowledge receipt of the letter, either by signing a duplicate or confirming by email.

 

Table: What to Include in a Written Warning Letter

 

Section	Details
Date	Date of the letter and the disciplinary hearing
Reason for Warning	Clear explanation of the conduct or performance issue
Expected Improvement	What the employee must do differently and by when
Duration	How long the warning will remain on record
Consequences	What could happen if there is no improvement
Right to Appeal	How and when the employee can appeal the decision

 

Section F: Can an Employee Appeal a Written Warning?

 

Employees in the UK have the right to appeal a written warning if they believe the decision was unfair, the disciplinary process was not followed correctly or new evidence has come to light. An appeal allows the employee to challenge the outcome of the disciplinary hearing and request a review of the decision. Employers must inform employees of this right when issuing the written warning and explain how the appeal can be submitted.

The right to appeal is part of a fair disciplinary process, as set out in the ACAS Code of Practice on Disciplinary and Grievance Procedures. While the Code is not legally binding, it is used by employment tribunals to assess whether an employer has acted reasonably. Failing to offer an appeal may lead to a finding of procedural unfairness, and if a tribunal finds the employer was at fault, compensation awarded to the employee can be increased by up to 25 per cent.

An employer should explain in the written warning letter how the employee can appeal, including the timeframe and contact details. Most organisations allow five or ten working days for the employee to lodge their appeal. The appeal should be submitted in writing and should clearly state the grounds for the appeal. These might include disagreement with the facts as presented, concern about how the hearing was conducted or evidence that was not previously available.

Once an appeal is received, the employer must arrange a separate appeal hearing. This meeting should be carried out by someone who was not involved in the original decision, ideally a manager who is more senior than the person who issued the warning. Where the organisation is small and this is not possible, the person handling the appeal must be as impartial as possible. The employee has the same right to be accompanied at the appeal hearing as they had during the disciplinary hearing.

During the appeal meeting, the employee should be given the opportunity to explain their concerns and present any supporting evidence. The appeal officer should review all relevant information, including the original decision, the employee’s response and any new material. It is important that the appeal is not treated as a formality; the employer must give proper consideration to whether the warning should be upheld, modified, or overturned.

After the hearing, the outcome should be confirmed in writing. The decision should be explained clearly, including the reasons for upholding or changing the original warning. If the appeal is successful, the written warning may be removed from the employee’s record or replaced with a lesser sanction. If the appeal is not upheld, the warning will remain in place for the original duration.

An appeal process helps ensure that employees are treated fairly and consistently. It gives them confidence that decisions are open to review and that their concerns will be heard. Employers who follow a fair and transparent appeal process are more likely to resolve issues internally and avoid disputes escalating unnecessarily.

 

Section G: Legal Risks for Employers

 

Issuing a written warning without following a fair and lawful process can have serious consequences for employers. Employment law requires that disciplinary action is reasonable and that employees are treated fairly throughout. Where a business fails to meet those standards, it may face legal claims, reputational harm and disruption to the wider workforce.

Skipping key procedural steps is one of the most common mistakes employers make when handling written warnings. For example, issuing a warning without giving the employee the chance to respond to the allegations, failing to conduct a proper investigation or not providing clear written confirmation of the decision can all amount to procedural unfairness. Even if the underlying issue is genuine, the way it is handled matters. An employment tribunal will look at both the reason for the disciplinary action and whether the process followed was fair and consistent.

If the employer’s conduct is unreasonable or undermines the employment relationship, the employee may resign and bring a claim for constructive dismissal. In such cases, the employee argues that the employer’s actions breached the trust and confidence essential to the employment contract. For example, where an employer issues a warning without evidence, or singles out an employee unfairly, the employee may feel they have no choice but to resign. If a tribunal agrees, the employer could be liable for compensation.

There is also a risk of an unfair dismissal claim where a written warning leads to dismissal and the warning itself was not justified. For instance, if an employer uses a first written warning as a stepping stone to dismissal, but the warning was based on weak evidence or flawed reasoning, the tribunal may find the dismissal unfair. Employers must ensure that warnings are based on fact, properly documented and that each step in the process is reasonable.

Another risk arises from inconsistency. If one employee receives a written warning for a particular issue, but another employee in a similar situation is treated more leniently, the employer may face a claim of unfair treatment or even discrimination. Consistent handling of disciplinary matters, supported by clear policies, helps reduce that risk.

Employers should also be aware that procedural mistakes can lead to increased compensation awards. If a tribunal finds that the employer failed to follow the ACAS Code of Practice, it can increase the compensation payable by up to 25 per cent.

 

Section H: Need assistance?

 

We help employers with all aspects of workplace disciplinaries, including guidance on when and how to issue written warnings. We can support you to ensure a fair and lawful workplace procedures are followed and to minimise the risk of tribunal claims. Our specialist HR consultants can also support with conducting workplace disciplinary investigations. For expert advice, contact us.

 

Section I: FAQs

 

Can I issue a written warning without a disciplinary hearing?

A written warning should only be issued following a fair disciplinary process. That includes an investigation, a formal hearing, and an opportunity for the employee to respond. Skipping these steps can lead to claims of unfair treatment.

 

How long should a written warning stay on file?

Most written warnings remain active for between six and twelve months, depending on the employer’s disciplinary policy and the nature of the issue. Once expired, the warning should not be relied on in future decisions, although it may be kept on record for reference.

 

Do I have to follow the ACAS Code of Practice?

While the ACAS Code is not legally binding, it is taken into account by employment tribunals. Employers who fail to follow the Code risk having to pay increased compensation if a claim is successful. Following it also helps ensure fairness and consistency.

 

Can an employee appeal a written warning?

Employees have the right to appeal a written warning. Employers must explain how the appeal can be made and deal with it promptly and fairly, ideally with someone not involved in the original decision.

 

Can a written warning lead to dismissal?

Yes, in some cases. If there is no improvement after a written warning, or if there is further misconduct or underperformance, an employer may progress to a final written warning or dismissal. Each step must be reasonable and follow a proper process.

 

What happens if I don’t handle the process correctly?

Failure to follow a fair procedure can lead to claims for unfair or constructive dismissal. It can also result in reputational damage and lower morale within the business.

 

Do employees have the right to be accompanied at a disciplinary hearing?

Employees are entitled to be accompanied by a trade union representative or a colleague. Employers must inform employees of this right in the hearing invitation.

 

Can I use a warning issued several years ago in a current decision?

Expired warnings should not be used to justify new disciplinary action. However, if there is a pattern of repeated behaviour, older records may be considered to show a history of conduct, but only with caution and proper explanation.

 

What should a written warning letter include?

The letter must state the reason for the warning, the required improvements, the timescale for change, how long the warning will remain in place, and the employee’s right to appeal.

 

Can a written warning be removed from an employee’s record?
Once the warning expires, it should not be relied on in disciplinary decisions. Some employers choose to remove it from the file altogether, while others keep it for reference. The approach should be consistent and in line with company policy.

 

Section J: Glossary

 

Term	Definition
Written Warning	A formal disciplinary measure issued to an employee when conduct or performance does not meet expected standards.
Disciplinary Hearing	A formal meeting where the employee is given the opportunity to respond to allegations before any disciplinary decision is made.
ACAS Code of Practice	Guidance issued by the Advisory, Conciliation and Arbitration Service setting out minimum standards for handling disciplinary and grievance procedures fairly.
First Written Warning	The initial level of formal warning issued for less serious misconduct or underperformance, usually active for 6–12 months.
Final Written Warning	A more serious warning issued either after a previous warning or for a more serious offence, often the last step before dismissal.
Constructive Dismissal	When an employee resigns in response to serious conduct by the employer that breaches the employment contract.
Unfair Dismissal	When an employee is dismissed without a fair reason or without a fair procedure being followed under UK employment law.
Appeal	The formal process by which an employee can challenge a disciplinary decision or sanction, including a written warning.
Right to Be Accompanied	The legal right of an employee to be accompanied by a colleague or trade union representative at a disciplinary or grievance hearing.
Live Warning	A warning that remains active on an employee’s record and can be considered in future disciplinary action during its validity period.