How to Handle Grievances: The ACAS Code of Practice Explained

When an employee raises a formal complaint—about unfair treatment, bullying, discrimination, or working conditions—that's a grievance. How you handle it matters enormously, both for your employee and for your legal position. In the UK, the ACAS Code of Practice on Disciplinary and Grievance Procedures sets the standard that employment tribunals expect employers to follow. Failure to follow it won't automatically land you in court, but if you do get there, a tribunal can increase compensation awards by up to 25% if you've unreasonably ignored the Code.

This guide explains how to handle grievances fairly, consistently, and in line with ACAS expectations—and what mistakes cost you.

What actually counts as a grievance?

Not every workplace complaint is a formal grievance. An employee might casually mention frustration about a deadline or ask why they weren't included in a meeting. Those are problems to address, but they're not necessarily grievances.

A grievance is a formal, written complaint about a workplace matter. Common ones include:

Unfair treatment by a manager
Bullying or harassment from colleagues
Discrimination based on a protected characteristic under the Equality Act 2010
Concerns about working conditions or safety
Disagreements about pay, benefits, or contract terms
How a policy has been applied (or misapplied)
Issues relating to absence management or statutory sick pay

The key difference: the employee is saying "I want this formally investigated and addressed," not just "I'm frustrated." If an employee raises a concern informally and you resolve it through a conversation, that's not a grievance—and you've probably saved yourself weeks of process.

But the moment an employee says they want a formal grievance, or puts their complaint in writing expecting formal action, you need to follow the Code.

The ACAS Code: five non-negotiable principles

The Code isn't complicated. It rests on five principles that sound obvious but matter in tribunal:

Deal with things promptly. Don't let a grievance sit in your inbox for six weeks while the employee stews. Delays make things worse and look bad in front of a judge.
Be consistent. If you handle one grievance one way and another grievance differently, you're creating ammunition for an unfair-treatment claim. Same facts, same process, every time.
Investigate properly. Gather documents, interview witnesses, understand the context. A sloppy investigation—or no investigation at all—makes your decision legally vulnerable.
Tell the employee what you've found and why. Don't ambush them with a decision. Let them know the basis of the complaint and give them a chance to respond.
Let them have a companion at formal meetings. The employee can bring a colleague or union rep. That companion can speak on their behalf and confer with them, but not answer questions in their place. This isn't a perk—it's a legal right.

These principles apply regardless of business size. A five-person team needs the same fairness as a five-hundred-person company. Scale your investigation to the seriousness of the complaint, but don't skip the fairness itself.

The grievance process: step-by-step

Step 1: The employee raises it formally

The employee should put their grievance in writing—an email, a form, a letter, something with a record. They should say what the problem is and, ideally, what they'd like to see happen as a result.

If the employee raises it verbally, take it seriously. Record what they said, confirm the details with them, and encourage them to follow up in writing (or do it yourself and send it to them to confirm).

Step 2: Arrange a meeting promptly

Once you have the grievance, acknowledge it quickly and arrange a meeting within a few working days. Don't sit on it.

Before the meeting, write to the employee confirming:

Date, time, location
That you're discussing their grievance
Their right to bring a companion (colleague or union rep)
An outline of the process

The meeting is about understanding the full complaint. Ask questions, listen, and note what you hear. This isn't a hearing yet—it's information-gathering.

Step 3: Investigate proportionately

After the meeting, investigate. "Investigate" doesn't have to mean weeks of formal depositions. It means:

Gather relevant documents and records
Interview witnesses
Review relevant policies and employment agreements
Consider any previous history

The investigator should be impartial—someone with no stake in the outcome. In a small business, that might be you, but approach it objectively and set aside personal feelings.

If the grievance is about you (the owner or sole manager), bring in an external HR consultant or mediator. Investigating your own complaint is not impartial and won't fly if this ends up in tribunal.

Step 4: Hold the formal hearing

Once investigation is done, hold a hearing. At this meeting:

Present your findings to the employee
Allow them to respond and add any information
They can be accompanied by a colleague or union rep
Their companion can speak on their behalf and confer with them
Take notes of what was said

If you need more time to consider the outcome, adjourn and reconvene. Don't rush a decision to save time.

Step 5: Decide and communicate in writing

Decide whether the grievance is upheld, partially upheld, or not upheld. Explain your reasoning in writing. If you're upholding it, say what you'll do about it. That might be:

Changing a working arrangement
Coaching or training for a manager
Disciplinary action against someone whose behaviour caused the grievance
An apology or policy review
Some combination

Whatever the outcome, the employee should understand why you reached it. A decision that looks arbitrary will haunt you.

Step 6: Offer the right to appeal

The employee can appeal if they disagree with the outcome. The appeal should be heard by someone different—ideally someone more senior. The appeal process mirrors the original: they get to present their case, you listen, you decide.

The appeal decision is normally final. But you must offer it.

Timescales (guidelines, not laws)

The ACAS Code says "promptly." That's vague, but here's what reasonable looks like:

Acknowledge the grievance within 1–2 working days
Hold the initial meeting within 5 working days
Complete the investigation within 2–4 weeks (depending on complexity)
Communicate the decision within 5 working days of the hearing
Hear the appeal within 2 weeks of receiving it

If the grievance is complex—multiple witnesses, sensitive issues, overlapping complaints—it may take longer. Keep the employee updated. Don't let them wonder whether you've forgotten about it.

Practical stuff for small business

When the complaint is about you

This is the hardest scenario. You're the owner, manager, and HR department. Suddenly you're also the defendant. Options:

Bring in an external HR consultant or employment law advisor to handle the process
If you have a trusted senior employee, ask them to lead the investigation
Use ACAS early conciliation as a neutral space to explore resolution

Whatever you do, don't investigate your own case. Find someone impartial. That person doesn't have to be a professional—just someone with no dog in the fight.

Try informal first (but always offer formal)

Many complaints can be resolved with a conversation. An apology, a change to working hours, a manager's reassurance—sometimes that's enough. There's no rule against informal resolution. It's faster and often better for the relationship.

But if informal doesn't work, or if the employee asks for formal proceedings, you must deliver. Refusing a formal grievance because you tried to resolve it informally is a mistake.

Documentation saves you

Document every stage:

The written grievance
Meeting invitations and notes
Investigation findings
The decision letter
The appeal (if one happens)

Store these securely with the rest of the employee's records. If a tribunal ever asks "why did you decide X?" you'll have a clear paper trail. If you have no notes, it looks like you made it up.

Mediation is an option

For grievances rooted in personality clashes or broken relationships—especially those involving manager behaviour or performance issues—formal mediation can work better than a tribunal-style hearing. A neutral mediator helps both sides talk through the issue and find common ground.

ACAS offers free mediation. There are also private mediators. Both parties have to agree to mediation—you can't force it. But when it works, it repairs relationships in a way that a formal process rarely does.

Early grievances during probation

If a grievance arises during an employee's probation period, follow the same process. The Code applies from day one. Probation doesn't mean you can skip fairness; it just means the employment relationship is conditional while both sides assess fit.

Mistakes that cost you

Ignoring the grievance. Hoping it goes away is not a strategy. Unaddressed grievances fester and escalate. Deal with them.

Not following the Code. The Code exists for fairness. Deviating from it without cause creates legal risk and invites tribunal to increase compensation by 25%.

Victimising the employee. If you punish, exclude, or demote an employee for raising a grievance, that's unlawful. Treat them professionally throughout.

Rushing to judgment. Investigate properly before deciding. A hasty conclusion based on incomplete evidence is both unfair and legally indefensible.

No appeal process. Always offer appeal. It's a basic requirement of the Code.

Frequently Asked Questions

Q: Does a grievance have to be in writing?

A: Ideally, yes. A written grievance gives you a clear record of what the problem is. If an employee raises a concern verbally, encourage them to write it down. If they won't, or can't, record the details yourself and confirm them with the employee. Verbal grievances are valid; written ones are just cleaner.

Q: Can I investigate the grievance myself if I'm part of the problem?

A: No. If the grievance involves you directly, your judgment is compromised. Bring in someone external—an HR consultant, an employment lawyer, or a mediator. The Code expects impartiality. A tribunal will expect it too.

Q: How long do I have to respond to a grievance?

A: The Code doesn't set a hard deadline, but "promptly" means days, not weeks. Acknowledge the grievance within 1–2 working days. Hold the meeting within 5 working days unless there's a good reason not to. If the process is going to take longer than expected, tell the employee why and give them a revised timeline.

Q: What if the grievance is about a colleague, not me?

A: Follow the same process. Investigate impartially. If the complaint is substantiated, take appropriate action against the colleague. That might include disciplinary steps depending on the seriousness of the misconduct.

Q: Do I have to give the grievance document to the person accused?

A: Yes. Fairness requires that the person being complained about knows what they're accused of and has a chance to respond. That's a core principle of the ACAS Code and employment law generally. You don't have to show them every piece of evidence, but they must know the core allegations.

Q: Can I sack someone for raising a grievance?

A: No. Firing or disciplining an employee for raising a grievance—even a trivial one—is unlawful victimisation. You can dismiss them for poor performance or misconduct unrelated to the grievance, but not because they complained. The law protects grievance-raisers.

Q: What happens if I ignore the ACAS Code?

A: You're not automatically in breach of law. But if a case goes to tribunal, the judge will compare your process to the Code. If you've ignored it without good reason, the tribunal is likely to find in the employee's favour and can increase any compensation award by 25%. Following the Code isn't just fair—it's smart risk management.

Q: How long should the whole process take?

A: Aim for 4–8 weeks from grievance to final decision, depending on complexity. Simple grievances (a misunderstanding, easily resolved) might be done in 2–3 weeks. Complex ones (multiple allegations, many witnesses, sensitive issues) might take 2–3 months. Keep the employee informed of progress.

The bottom line

Grievance handling isn't complex. It's about fairness, consistency, and documentation. Follow the ACAS Code, treat the employee professionally, investigate properly, and keep records. You'll protect your business, support your employee, and build a workplace where problems are addressed rather than buried.

If you're stuck, ACAS itself is a free resource. Their guidance is comprehensive, and early conciliation can help resolve disputes before they escalate to tribunal. Use it.