ACAS codes of practice are not legally binding in the way that statutes are. But they carry significant legal weight: employment tribunals are required to take them into account when assessing whether an employer acted reasonably, and can adjust compensation by up to 25% where either party has unreasonably failed to follow them.

For managers – who are the primary actors in disciplinary and grievance processes – the ACAS codes of practice define the procedural standard they are expected to meet. Meeting that standard requires training.

The ACAS Code on Disciplinary and Grievance Procedures

The ACAS Code of Practice on Disciplinary and Grievance Procedures is the most widely cited of the codes and the one with the most direct bearing on manager training. It applies to disciplinary situations – including warnings and dismissals – and to the handling of grievances, including complaints about harassment, bullying and workplace misconduct.

The Code sets out the steps that constitute a fair process: investigation before action, notification of the concern and the right to respond, a hearing with the right to be accompanied, a decision with reasons, and a right of appeal. Each of these steps involves judgment calls that managers make in real time. Without training, those judgments are made on instinct – and instinct frequently diverges from the Code.

Where untrained managers typically fail the Code

Tribunal records and ACAS guidance consistently identify the same procedural failures by untrained managers:

• Conducting an inadequate investigation – or no investigation – before initiating disciplinary action
• Failing to inform the worker of the specific allegation clearly and in advance of the hearing
• Not offering the right to be accompanied to a hearing or informal meeting that should have been formal
• Conflating the investigatory and decision-making roles – allowing the manager who investigated to also impose the sanction
• Imposing a disproportionate sanction without reference to the worker’s record or the seriousness of the conduct
• Failing to allow a genuine right of appeal or hearing the appeal without fresh consideration

Any of these failures can result in a tribunal finding of procedural unfairness and an ACAS uplift applied to compensation, even where the dismissal or sanction was substantively justified.

The ACAS Code and whistleblowing: the overlap managers must understand

A significant source of tribunal exposure arises where a manager initiates or accelerates disciplinary action against a worker who has recently made a protected disclosure. Under PIDA, dismissal in those circumstances is automatically unfair. If the disciplinary process also fails to follow the ACAS Code, the employer faces both an automatic unfair dismissal claim and the ACAS uplift on top.

Managers need to understand that the ACAS Code and PIDA operate in parallel – and that a procedurally compliant disciplinary process does not cure the underlying PIDA problem if the action was taken in response to a whistleblowing disclosure. Training that covers the ACAS Code without covering the whistleblowing context leaves managers with a partial picture that is particularly dangerous in practice.

The ACAS Code on handling grievances: harassment and disclosure

The ACAS grievance Code applies when workers raise formal concerns about their treatment. Harassment and bullying complaints are the most common grievance type managers encounter – CIPD research in 2024 found that 1 in 4 workers had experienced bullying or harassment in the workplace.

Following ERA 2025, a grievance raising sexual harassment concerns may simultaneously be a protected disclosure under PIDA. Managers who treat such a grievance purely as a procedural HR matter – without recognising the whistleblowing dimension – risk subjecting the worker to detriment under a framework they did not know applied. Training that integrates the ACAS grievance Code with the post-ERA 2025 whistleblowing framework is no longer optional in well-governed organisations.

The ACAS Code requires employers to deal with grievances promptly, investigate properly, hold a meeting to discuss the grievance, and offer an appeal. Where a grievance also constitutes a protected disclosure, these procedural steps need to be taken in a way that protects the confidentiality of the reporter – a requirement that PIDA imposes and that the ACAS Code does not displace.

ACAS codes of practice guidance on discipline and grievance: beyond the Code

ACAS also publishes non-statutory guidance that supplements the Code – covering topics including managing difficult conversations, investigations in the workplace, and discipline and grievances at work. This guidance is not subject to the statutory uplift mechanism but provides practical detail on how the Code’s requirements should be met in practice.

For manager training purposes, ACAS guidance is particularly useful for two areas: the conduct of workplace investigations, and how to handle sensitive disclosures including harassment complaints. Investigations Training that draws on ACAS guidance alongside legal frameworks equips managers to meet both the procedural and practical standard the Code requires.

Other ACAS codes relevant to manager training

ACAS Code on Settlement Agreements

Where a manager is involved in discussions about ending an employment relationship, the ACAS Code on Settlement Agreements applies. Managers who initiate settlement discussions with a worker who has recently made a protected disclosure create both a PIDA detriment risk and, if the settlement process is mishandled, a further breach of the settlement agreement Code. Training on when and how settlement discussions can be properly initiated is relevant for managers with operational responsibility for employment decisions.

ACAS guidance on managing people with mental health conditions

Where disciplinary or grievance situations involve workers with mental health conditions, the EHRC’s guidance on disability-related adjustments and ACAS guidance on mental health at work both bear on how managers should proceed. The failure to consider reasonable adjustments in a disciplinary process involving a disabled worker is both a direct Equality Act issue and a potential ACAS Code procedural failure. Training that addresses the intersection of disciplinary procedure and disability obligations equips managers to avoid a category of claim that is both frequent and expensive.

What ACAS Code-compliant manager training looks like

Training that genuinely equips managers to comply with ACAS codes should address:

• The five-step disciplinary process under the Code: investigation, notification, hearing, decision, appeal
• How to conduct a fair investigation – including the role separation between investigator and decision-maker
• The right to be accompanied and when it applies
• How to handle grievances involving harassment or potential protected disclosures under PIDA and ERA 2025
• The 25% ACAS uplift mechanism and when it applies
• The intersection of ACAS procedures with whistleblowing protections, disability obligations and the WPA 2023 positive duty
• Practical scenarios that test application of the Code in realistic workplace situations

Training that covers the Code as a set of steps, without equipping managers to apply it in the ambiguous and contested situations it is most frequently invoked in, does not meet the standard. Scenario-based, facilitated training that draws on real-world case material is more effective than step-by-step compliance instruction – and more useful to the managers who need to apply the Code under pressure.

Related resources

Legal Obligations for Manager Training in the UK (hub): https://www.safecall.co.uk/resource/legal-obligations-for-manager-training-in-the-uk/

Handling Whistleblowing Disclosures – A Manager Guide: https://www.safecall.co.uk/resource/what-is-the-legal-framework-for-handling-whistleblowing-disclosures-in-the-uk/

Workplace Investigation Training in the UK: https://www.safecall.co.uk/service/investigation-training/

Whistleblowing Training for Managers: https://www.safecall.co.uk/service/whistleblowing-training-for-managers-online-and-on-site/

Safecall’s training for managers

Safecall’s facilitated training courses address the ACAS codes of practice directly alongside the legal frameworks they intersect with. Listen Up – Whistleblowing for Managers (CPD Certified; online half day or in-person full day) covers the whistleblowing and grievance dimensions. Investigations Training (CPD Certified; online half day or in-person full day) covers the investigatory and disciplinary procedure requirements in depth, led by a former police officer with 25+ years of investigative experience. Both courses use real-world case material and are available with bespoke tailoring.

Find out more about Safecall’s training courses at safecall.co.uk/service/compliance-training/ or contact the team at learning@safecall.co.uk | +44 (0) 191 516 7720

Sources and further reading

ACAS – Code of Practice on Disciplinary and Grievance Procedures: acas.org.uk/acas-code-of-practice-for-disciplinary-and-grievance-procedures

ACAS – Discipline and grievances at work (non-statutory guidance): acas.org.uk/discipline-and-grievances-acas-guide

ACAS – Code of Practice on Settlement Agreements: acas.org.uk/acas-code-of-practice-settlement-agreements

ACAS – Conducting workplace investigations: acas.org.uk/conducting-workplace-investigations

CIPD – Harassment and Bullying at Work, 2024: cipd.org/uk/knowledge/reports/harassment-bullying-work/

Public Interest Disclosure Act 1998 (as amended): legislation.gov.uk/ukpga/1998/23

Employment Rights Act 2025: legislation.gov.uk/ukpga/2025