Human resource professionals are often confronted with anonymous telephone calls, letters or e-mails containing allegations regarding an employee's conduct. As opposed to a complaint from an identified source, the company is often hesitant to initiate an investigation of the circumstances when the complaining party is unwilling to identify themselves. The employer may suspect that the complaint is made for an ulterior motive, such as a co-worker or former girlfriend/boyfriend looking to retaliate against the subject of the complaint.Despite these concerns, employers should not adopt a rule that absolutely excludes investigation of anonymous complaints. Based on the specific circumstances, the complaint may contain enough detail and deal with matters of such seriousness that the employer feels compelled to investigate despite the source of the complaint. In some cases, the anonymous complaint may be only part of multiple allegations or evidence regarding the employee's conduct, and the overall circumstances may compel further action by the employer.However, in less dire cases, employers can treat anonymous complaints differently from those made from an identified source. If the employer concludes that the complaint lacks credibility due to the inability to obtain additional information from the source, it can be a reasonable response not to investigate or take follow-up action absent other confirmation of the claims. In general, employers have a legal duty to act reasonably under the circumstances, and such reasonableness may include a decision not to chase down every anonymous complaint received by the company.If the employer has a complaint policy, this distinction can be explained, and complaining parties can be cautioned that their failure to identify themselves may result in the company declining to take action in response.