Sit back son, while I lay some knowledge upon you. There are excepted tax rates; this refers to luxury products. Chocolate covered biscuits are considered a luxury item; whereas a chocolate covered cake is not subject to these taxes. There was a famous court case, regarding Jaffa Cakes - a chocolate-covered sponge confectionery. The point of definition is that a biscuit goes soft when they are stale; and cakes go hard when they are stale.