A coworker keeps treating me badly and I've decided to put it in writing to HR. How do I write the complaint so it's taken seriously?

Example complaint email (190 words)

“Subject: Formal complaint about conduct of Derek Hall

Dear Laura,

I am writing to make a formal complaint about repeated conduct by my coworker Derek Hall on the warehouse team.

- Sept 14, morning shift meeting: in front of six colleagues, Derek called my pick count “pathetic”. Ana Ruiz and Sam Cole were present. - Sept 29 and Oct 2: Derek changed my break slot on the rota without asking our lead. The rota history shows both edits. - Oct 8: Derek told a new team member, Priya, that I would be “gone by Christmas”. Priya mentioned it to me the same day.

I raised this with our lead, Tom Baker, on Oct 1. The break changes happened again after that conversation.

This has made me dread shared shifts, and I have twice swapped shifts to avoid him.

I would like to meet to discuss this, and I am asking that only the shift lead edits break slots. I can provide the rota screenshots.

Kind regards, Maria Lopez Picker, morning shift”

Every line can be checked: a date, a place, a witness or a record. Nothing calls Derek a name.

Facts that hold up, and words that hurt your case

HR has to look into what can be checked. A complaint full of conclusions (“he's toxic”, “a hostile person”) asks HR to share your opinion; a complaint full of dated events lets them find it themselves.

Turn each feeling into an event:

- “He's always rude to me” becomes “On Sept 14 he called my work ‘pathetic’ in front of six people.” - “He sabotages my schedule” becomes “He changed my break slot on Sept 29 and Oct 2; the rota history shows it.” - “Everyone knows” becomes the names of the people who saw it.

Say how it affects your work, once and plainly: swapped shifts, missed targets, time off. Leave out guesses about why he does it, other people's private lives and anything you heard third-hand without saying so.

If the behavior involves harassment or discrimination linked to race, sex, religion, age, disability or another protected trait, say so in plain words. That can change how the employer must handle it, and it matters for any later step outside the company.

UK readers: a written grievance

In the UK the formal version is usually called a grievance. Acas, the UK's workplace advice service, says on its grievance pages (read 15 Oct 2026) that raising a problem informally first is usually a good idea, that a formal grievance should be put in writing to whoever is most appropriate under your employer's policy, and that it should cover what the grievance is about, any evidence and what you want your employer to do. It also advises raising it as soon as you can.

If your problem is with your line manager, the same pages suggest going to another manager or HR instead. Acas links to its own grievance letter template, and Citizens Advice also offers help with writing one.

The example above works as a grievance with the subject changed to “Formal grievance” and a sentence saying you are raising it under the company's grievance procedure.

When to go beyond HR, and what this page cannot do

HR works for the employer. Most complaints are handled fairly, but it helps to know where the outside routes are before you need them.

In the US, discrimination and harassment complaints can go to the EEOC, and its own site lists filing deadlines counted from the date of the event (180 days, extended to 300 in some places). If a protected trait is involved, read that page or talk to an employment lawyer early rather than waiting for the internal process to finish. In the UK, Acas publishes guidance on the steps after a grievance, including appeals.

The Email format drafts the message from your facts and nothing else; it does not judge your case or give legal advice. Formal tone keeps the language neutral, and Medium length (120 to 250 words) fits most complaints. A red pen pass removes padding such as “I hope this email finds you well”, which reads oddly in a complaint.