When the sole owner of a dental practice in Red Deer, Alberta settled shares of the professional corporation into a family trust for the benefit of 3 adult children as part of the 2024 estate freeze, the tax deferral achieved through the corporate reorganization was not permanent but rather subject to an important time limit built into Canadian tax law. The family had successfully structured the freeze so that the $2.8 million fair market value of the practice was locked into the owner's preference shares, while growth shares in the trust would capture future appreciation for the children. What the family now needed to understand, however, was that the Income Tax Act imposes a rule that treats trusts as though they have sold their assets after 21 years, even when no actual sale has occurred. This rule, commonly called the 21-year deemed disposition rule, would require the trust to recognize any accumulated gains on the growth shares at the 21-year anniversary of the trust's creation, potentially triggering a significant tax bill unless the family planned ahead. The mechanics of navigating this rule and maintaining proper compliance over the life of the trust represent essential knowledge for any small business owner who has implemented an estate freeze using a trust structure.