How to Conduct an Internal HR Investigation

10/23/2025

Every HR professional eventually faces it — a workplace complaint that demands a fair, thorough investigation. Whether it involves harassment, discrimination, or policy violations, your response defines both compliance and culture. This guide walks you through how to conduct an internal HR investigation step-by-step — from intake and interviews to documentation and corrective action — so you can protect employees and your organization.

Why HR Investigations Matter for Compliance

A well-conducted internal investigation is one of HR's most critical functions. It is the primary mechanism for addressing potential legal violations and upholding a safe, respectful workplace. When an employee raises a concern about harassment, discrimination, or retaliation, federal laws like Title VII of the Civil Rights Act, the Americans with Disabilities Act (ADA), and the Family and Medical Leave Act (FMLA) create an affirmative duty for the employer to act.

Ignoring a complaint or handling it poorly can lead to costly lawsuits, EEOC complaints, and significant damage to your organization's reputation. More importantly, a fair and confidential process prevents retaliation, demonstrates a commitment to ethical standards, and builds the employee trust necessary for a healthy workplace culture. Your investigation is not just about finding facts; it’s about showing your workforce that their concerns are taken seriously.

When to Launch an Internal HR Investigation

Knowing when to initiate a formal investigation is the first critical judgment call. Not every workplace disagreement requires a full-scale inquiry, but many situations legally demand one.

Recognizing a Formal or Informal Complaint

The duty to act is triggered as soon as the employer knows or should have known about potential misconduct. A complaint does not have to be a formal, written document submitted to HR. It can be a verbal comment made to a supervisor, an email detailing unfair treatment, or even an anonymous tip. Document the initial report immediately, capturing who reported it, when, what was alleged, and who was involved. This initial intake form is the first piece of your audit trail.

Determining Whether the Complaint Requires Investigation

Once a complaint is received, you must assess its severity and credibility to determine the next steps. Allegations involving harassment, discrimination, safety violations, retaliation, or theft almost always require a formal investigation. If the complaint involves a minor policy infraction or a simple misunderstanding, an informal mediation or conversation may suffice. However, when in doubt, it is always safer to proceed with a formal investigation. If the allegations are particularly severe or involve high-level executives, it is wise to consult with legal counsel to determine if an outside investigator is needed.

Step 1 — Plan the Investigation

A successful investigation is a well-planned one. Before you conduct a single interview, take the time to create a clear plan. This avoids scope creep and ensures a consistent, defensible process. Your plan should:

• Identify the allegation type: Is this a violation of the anti-harassment policy, a potential FMLA interference claim, or a safety concern? Knowing this helps you identify the relevant policies and legal standards.
• Define the scope and timeline: What is the core question you need to answer? Who are the key individuals to interview? What is a realistic timeframe for completing the investigation?
• Assign an impartial investigator: The investigator must be neutral and unbiased. Avoid assigning someone who has a close personal relationship with any of the involved parties or a vested interest in the outcome.
• Prepare interview outlines and document templates: Create a list of open-ended questions for the complainant, witnesses, and the accused. Prepare standardized templates for interview notes and a final report to ensure consistency.

Step 2 — Gather Relevant Information

The investigation's credibility rests on the quality of the evidence you collect. This process goes beyond interviews and includes gathering all relevant physical and electronic documentation.

Collect Documents, Emails, and Policies

Begin by collecting all pertinent documents. This could include performance reviews, timecard records, email chains, text messages, security footage, and copies of the specific company policies that were allegedly violated. Review the personnel files of the involved parties to understand their employment history and any prior issues. When securing electronic evidence like emails or instant messages, partner with your IT department to ensure you can retrieve the data without breaching privacy protocols.

Maintain Confidentiality and Chain of Custody

Confidentiality is crucial. Information about the investigation should be shared only on a strict, need-to-know basis. Create a secure, confidential investigation file that is stored separately from general personnel records. This is a legal requirement for any medical information gathered, which must be kept separate under ADA, FMLA, and GINA rules. Maintain a "chain of custody" log for any physical evidence to track who has accessed it and when.

Step 3 — Conduct Interviews Professionally

Interviews are the heart of most investigations. The goal is to gather facts, not to intimidate or pass judgment. A professional, structured approach is essential.

Interview the Complainant First

Always begin by interviewing the person who made the complaint. Let them tell their story in their own words without interruption. After they have provided their full narrative, you can ask clarifying, open-ended questions like, "Can you tell me more about that?" or "Who else was present when that happened?" Assure them of the company’s strict anti-retaliation policy and manage their expectations about confidentiality, explaining that you will only share information as necessary to conduct a thorough investigation.

Interview Witnesses Objectively

Next, interview any potential witnesses identified by the complainant or discovered during your evidence gathering. When speaking with witnesses, state the purpose of the interview broadly (e.g., "We are looking into a workplace concern") without revealing sensitive details of the complaint. Ask open-ended questions about what they have personally seen or heard. Avoid leading questions that suggest a desired answer, such as, "You saw John yelling, didn't you?" Instead, ask, "Describe what you observed in the breakroom last Tuesday."

Interview the Accused Last

The final interview should be with the person accused of misconduct. This interview should be handled with care and professionalism. Inform them of the complaint in a factual, non-accusatory manner, summarizing the allegations without revealing who made them. Provide them with a full opportunity to respond to each allegation. Pay close attention to their tone, demeanor, and the details of their response, documenting it all carefully. Conclude by instructing them not to retaliate against anyone and not to discuss the matter with coworkers.

Step 4 — Analyze the Findings

Once all interviews are complete and evidence is gathered, the investigator must analyze the information to reach a conclusion.

Your role is to weigh the evidence and determine what is "more likely than not" to have occurred. This is known as the "preponderance of the evidence" standard, which is the standard used in civil litigation. It is a lower bar than the "beyond a reasonable doubt" standard used in criminal cases.

To make this determination, evaluate the credibility of the testimony. Was the information firsthand or hearsay? Was the testimony consistent? Did the individual have a motive to be untruthful? Compare the testimony to the documentary evidence. Where do the stories align or diverge? It is helpful to keep a separate file for your own analysis and opinions, keeping the official investigation file purely factual.

Step 5 — Document and Report the Outcome

The final investigation report is the official record of the process and its conclusions. This document is a critical piece of your legal defense should the matter escalate.

Draft a Clear, Factual Report

The report should be well-organized and written in clear, objective language. Avoid legal jargon, subjective opinions, or emotional statements. A standard report should include:

• An overview of the complaint.
• The scope of the investigation.
• A summary of the evidence gathered (documents and interviews).
• A summary of the findings of fact for each allegation.
• A conclusion based on the preponderance of the evidence.
• A recommendation for corrective action, if applicable.

Store Records Securely

The final report and the entire investigation file must be stored securely and confidentially. These records should never be placed in an employee's main personnel file. Access must be strictly limited. As a reminder, under ADA and FMLA confidentiality rules, any medical information must be kept in a separate, locked file with even tighter access controls.

Step 6 — Take Corrective Action

If the investigation concludes that a policy was violated, the employer must take prompt and appropriate corrective action. The action should be designed to stop the misconduct and prevent it from happening again.

The level of discipline should be consistent with company policy and proportionate to the severity of the offense. Actions can range from a verbal warning or mandatory retraining to suspension or termination of employment. Once a decision is made, communicate the outcome to the necessary parties. While you cannot share the specific disciplinary details with the complainant, you should inform them that the investigation is complete and that appropriate action has been taken. Finally, you must take active steps to prevent any retaliation against the complainant or witnesses.

Step 7 — Follow-Up and Prevent Future Issues

The investigation doesn't end with the final report. A thorough process includes follow-up and prevention.

A few weeks after the investigation concludes, conduct private check-ins with the complainant and the accused (if they are still employed) to ensure there has been no further misconduct or retaliation. If the investigation revealed a gap in your policies or a need for broader training, use it as an opportunity to improve. Update your employee handbook, create a new training module for managers, or offer support resources like EAP to the affected teams. This closes the loop and turns a reactive event into a proactive improvement.

Common Mistakes in HR Investigations

Even experienced HR professionals can make mistakes. The most common errors include:

• Failing to act promptly: Delaying an investigation can be interpreted as indifference and may violate legal requirements.
• Bias in investigator selection: Choosing an investigator who cannot be impartial taints the entire process.
• Over-disclosing confidential details: Sharing sensitive information with individuals who do not have a need to know.
• Incomplete or missing documentation: Failing to document interviews or decisions, leaving the organization vulnerable.

Building a Legally Compliant Investigation Framework

A consistent and legally sound investigation process relies on a strong framework. This starts with a clear internal investigation policy that is aligned with the requirements of Title VII, ADA, FMLA, and other employment laws. Document every step of every investigation using a standardized process and templates. Finally, ensure your investigation process is integrated with your leave and accommodation management protocols, so that issues like FMLA retaliation or ADA accommodation denials are handled with the same rigor.

HR Investigation Best Practices for 2025

As workplace dynamics evolve, so do best practices for investigations. For 2025, focus on:

• Emphasizing psychological safety: Create an interview environment where employees feel safe to speak truthfully without fear of judgment or retribution.
• Standardizing documentation templates: Use checklists and templates to ensure every investigation is equally thorough.
• Training managers on recognizing reportable behavior: Empower supervisors to be your eyes and ears, teaching them to identify and escalate potential issues before they become major problems.

Key Takeaways for HR Teams

Conducting a compliant, fair, and well-documented investigation is one of HR’s most critical responsibilities. It is a complex process that requires careful planning, objectivity, and meticulous attention to detail. By developing and adhering to a consistent process — from intake and planning to resolution and follow-up — you can navigate workplace complaints effectively, ensure compliance, and maintain a culture of fairness and trust.

Follow our step-by-step HR investigation checklist to strengthen your compliance process.