Captive insurance remains one of the most closely examined tax planning strategies in use today, not because it is inherently flawed, but because small missteps can carry outsized consequences. Many taxpayers assume that careful formation and proper documentation are enough to protect the intended tax outcome. A recent Tax Court decision, Kadau v. Commissioner, serves as a reminder that those assumptions deserve closer scrutiny. The court’s analysis did not hinge on whether captive insurance can work, but on how a specific arrangement actually functioned in practice. For tax professionals advising clients who rely on micro-captives, the case raises important questions about where structures tend to break down, why some arrangements attract IRS attention while others do not, and what really separates a defensible captive from one that invites challenge.