Loss carryforwards and other tax attributes are valuable assets because they can shelter taxes. As such, loss utilization has always been a staple of good tax planning. The Income Tax Act and the CRA’s administrative policies have generally accepted loss utilization planning within affiliated and related parties. On the other hand, the Act has always had provisions against arm’s length loss trading transactions whereby one taxpayer in effect makes use of another’s unused tax attributes. Prior to March 21, 2013, these rules were referred to as the “acquisition of control” rules and they applied only to corporations. However, in recent years, there are a proliferation of non-corporate vehicles that carry on substantial activities traditionally undertaken only by corporations. In response, the Department of Finance introduced a new “loss restriction event” concept in new section 251.2, effective March 21, 2013, that essentially expands the old acquisition of control regime to partnerships and trusts. At first glance, the rules in section 251.2 appears to be of limited relevance to ordinary trust and estate planning due to the affiliated person exceptions provided. However, there are traps for the unwary contained in these rules.