How to Run a Workplace Investigation in California: Seven Steps From Complaint to Closure

Run a workplace investigation in seven steps: take the complaint in writing, protect people in the interim, plan who you will interview and what you will collect, interview every person the same way, log the evidence, write findings of fact against a standard you state in advance, and follow up at 30 and 90 days. California employers are expected to take all reasonable steps to prevent discrimination and harassment and to act on problems once they know about them. A documented process is how a small employer shows it did.

I am Mac Malbrough. I hold a J.D. and an MS-HRM, I am not an attorney, and this is general information about HR practice, not legal advice. I checked the statutes cited below on the California Legislative Information site, and I say plainly where a point is practice guidance and not statute. For a complaint that involves a serious allegation, an executive, or a threatened lawsuit, bring in an employment attorney before you start.

Why does a small employer need a written investigation process?

Because the complaint is the easy part. Someone tells a manager that a coworker made comments, a supervisor treated them differently after they raised a pay concern, or a team is afraid of one person. The hard part is what happens in the next ten days. Without a process, the manager talks to the accused in the hallway, the complainant hears nothing, and a month later someone is fired for an unrelated reason that looks, from the outside, like retaliation.

The California Fair Employment and Housing Act makes it unlawful for an employer to fail to take all reasonable steps necessary to prevent discrimination and harassment from occurring (Government Code Section 12940(k)). The same section makes it unlawful to retaliate against a person for opposing practices the act forbids or for filing a complaint (Section 12940(h)). Those two lines are why an investigation exists. It is the step that shows you took the complaint seriously, and it is the record you will want if anyone later asks what you did.

Step 1: Take the complaint in writing

Start with an intake record that captures the date, who received the complaint, the name of the person complaining, the people involved, what is alleged, when and where it happened, and who saw it. If the complaint came verbally, write it down and read it back to the complainant. Do not promise confidentiality you cannot keep. Say instead that you will share information only with people who need it to investigate and respond.

Decide in the first day who will investigate. It should be someone with no stake in the outcome and no reporting line to the accused. In a very small company, that may mean an outside investigator or a consultant. Outside investigators who are not attorneys generally need a private investigator license in California, with exemptions for employees and for attorneys, so confirm the status of anyone you hire before they start (Business and Professions Code Sections 7521 and 7522).

Step 2: Protect people in the interim

Ask whether the complainant needs distance from the accused while you investigate: a schedule change, a different reporting line, a work-from-home arrangement, a paid leave. Offer the option and let the complainant choose, so that the protective step never looks like a penalty. Do not move or suspend the complainant against their wishes, and do not change their pay, hours or duties because they complained.

For the accused, remind them in writing that the matter is under review, that no conclusion has been reached, and that retaliation of any kind is prohibited. Keep the tone neutral. A fair process protects the accused as much as the complainant.

Step 3: Write a short plan

A one-page plan beats a thick binder. It should list the allegations as separate questions, the people to interview in order, the documents and messages to collect, the policy or law that applies, and a target date for each step. Write down the standard you will use to decide. The Civil Rights Department’s harassment prevention guidance describes findings as a decision about whether it is more likely than not that the conduct occurred, and that is the standard I recommend naming in your plan. That is practice guidance, not a statute.

Plan the order carefully. Interview the complainant first, then witnesses, then the accused last, so that the accused can respond to everything you have learned. Prepare the same core questions for each person so that every interview covers the same ground.

Step 4: Interview every person the same way

Begin each interview with the same opening: who you are, why you are meeting, that it is a fact-finding process, that retaliation is prohibited, and that the person should tell the truth and keep the conversation confidential to the extent they can. Ask open questions and let the person tell the story before you test it with specifics. Ask for names of anyone else who saw or heard something, and for any documents, texts or photos.

• Have a second person take notes, so the interviewer can listen.
• Do not record a confidential conversation without every party’s consent. California requires consent from all parties to record a confidential communication (Penal Code Section 632).
• If the workforce is unionized, an employee may ask for a representative at an investigatory interview, so check your obligations before you begin.
• Close by asking whether there is anything else you should know and whether the person has questions about the process.

Step 5: Collect and log the evidence

Keep an evidence log with an entry for each item: what it is, where it came from, who collected it, when and where it is stored. Collect messages, schedules, time records, prior complaints and any policy the conduct might violate. Preserve what exists before anyone has a chance to delete it, and put a hold on automatic deletion if your systems have one.

Records matter beyond the investigation. California requires employers to keep personnel and employment records for at least four years, and records connected to a verified complaint have to be kept until the matter is resolved (Government Code Section 12946). Employees also have a right to inspect and copy their personnel records within 30 calendar days of a request (Labor Code Section 1198.5), so assume that anything in the file may be read by the person it concerns.

Step 6: Write findings of fact

Findings are a short written decision for each allegation: substantiated, not substantiated, or inconclusive, with the facts that support the conclusion. Write facts, not legal conclusions. “Two witnesses reported hearing the comment, and the accused did not deny saying it” is a finding of fact. “The accused harassed the complainant” is a legal conclusion that belongs to a court or an agency, not to an employer’s HR file.

Then decide on the response. If the conduct violated policy, take corrective action that fits it, from coaching to termination, and apply the same standard you would apply to anyone else in the same position. If the allegation was not substantiated, say so without implying the complainant lied. Tell both people, in separate conversations, what you can share: that the process is complete and that the employer will protect against retaliation.

Step 7: Follow up at 30 and 90 days

The investigation does not end with the findings letter. Check back with the complainant at about 30 days and again at about 90 days to ask whether the conduct has stopped and whether anything has changed in how they are being treated. The Civil Rights Department’s guidance recommends follow-up of this kind, and I recommend it because the second complaint, the one about retaliation, is the one employers lose. Timing matters in retaliation claims, and I explain how in my guide to the 90-day retaliation presumption.

Make each follow-up a calendar entry and a short note in the file. If anything is wrong, document what you did about it.

What about retaliation?

Retaliation is where the second claim comes from. Besides Section 12940(h), California protects employees who complain about wages or unsafe conditions and those who disclose unlawful activity (Labor Code Sections 98.6 and 1102.5). Before any adverse action against a person who has complained, whether the complainant, a witness or the accused, ask yourself whether the action would have happened anyway and whether the record shows it. If you are not sure, talk to an employment attorney before you act. My guide to performance improvement plans and my piece on termination documentation cover the documentation habits that matter here.

What tools make this easier?

The seven steps need paperwork every time: an intake form, interview guides, an evidence log, a findings memo and the letters that go to each party. I built the Workplace Investigation Kit: 14 Forms, 9 Letters and a Tracker for $39 so a small employer does not have to draft them in the middle of a complaint. If you want the whole discipline sequence in one download, the Discipline and Exit Bundle pairs the investigation kit with the performance review and PIP set, the termination and offboarding checklists and the hard conversation scripts for $169. These are templates and general information, not legal advice.

Keep investigation materials apart from the personnel file, as I explain in the six employee files and what belongs in each.

What should you do this week?

1. Name who investigates, and who backs them up if the complaint involves them.
2. Write the one-page plan template and the interview opening you will use every time.
3. Check how your systems retain messages and documents, and who can place a hold.
4. Put 30 and 90 day follow-up reminders in a calendar that more than one person can see.
5. Decide in advance which complaints go straight to an employment attorney.

If you want help building the process for your company, the HR compliance check-up is the place to start, and the free live sessions cover California compliance topics through the year.

A fair investigation is also how HR earns credibility, covered in how HR builds credibility inside a small company.

A fair process is also how HR earns trust, covered in what builds trust between employees, leaders and HR.

Related reading: what to do when HR is asked to defend a decision it disagrees with.

Sources

• Government Code Section 12940
• Government Code Section 12946
• Labor Code Section 1198.5
• Labor Code Section 1102.5
• Penal Code Section 632
• Business and Professions Code Section 7522
• California Civil Rights Department, Harassment Prevention Guide (2025), for the findings standard and follow-up timing, which are practice guidance

McKinley holds a J.D. but is not a licensed attorney. Articles here are general information, not legal advice. For your specific situation, talk with an employment attorney.

Data current as of November 2026. Sources are linked where each figure appears.