When an individual owns less than 100% of a property, partnership, LLC or business, it is presumed it will be harder to sell and less valuable than if they owned 100%. 

Based on this assumption, BTI calculates how much the individual’s interest should be discounted because it is a partial interest.  Typically, this is applicable when a person dies and their estate holds such partial assets, or when a person wishes to donate such partial interests as part of their estate planning.