The distinction turns on whether the bar or block contains a filling — a center of different composition such as caramel, cream, or fruit — enclosed within the chocolate. A bar that is uniform chocolate throughout is unfilled (180632), while one with a distinct interior filling is classified as filled (180631). Both subheadings apply only to presentations of 2 kg or less.

A preparation leaves 1806 when cocoa is not a defining characteristic of the product. For example, a flour-based baked good with a small cocoa addition may fall under heading 1905, and a cocoa-flavored ice cream falls under heading 2105. The chapter notes and the relative weight of cocoa versus other ingredients guide the classification of borderline products.