Which of the following is NOT a common type of case for private investigators?

Tax evasion is not typically considered a common type of case for private investigators. While private investigators may occasionally be involved in cases related to tax evasion, this area is usually within the jurisdiction of government agencies such as the Internal Revenue Service (IRS) or local tax authorities. These organizations have the legal authority and resources to conduct extensive investigations into tax-related matters, including access to financial records and other sensitive information.

In contrast, infidelity, missing persons, and fraud are more frequently handled by private investigators. Infidelity cases often involve surveillance and gathering evidence of a spouse's or partner's activities. Missing persons investigations require finding individuals who have disappeared, which can involve interviewing family members, checking social media, and tracing whereabouts. Fraud cases may involve investigating scams or financial deceit, which private investigators are well-equipped to handle through interviews, background checks, and financial analysis. Thus, while tax evasion can be addressed in some contexts, it does not fall into the category of common private investigator cases.