An approach for transforming a starting list of purchase types into a selection list of valid purchase types by employing a configurable rule is presented. A unit price and commodity code are received for an item whose purchase is being charged to an account. Based on a category of the item, a starting list including purchase types is generated. Each purchase type specifies a corresponding accounting function. A rule set is identified in a table that associates the rule set with purchase type(s) specifying corresponding accounting functions. Identifying the rule set includes determining that the purchase type(s) are in a maximal subset of the purchase types included in the starting list. Based on the rule set and the unit price, a rule is identified in another table. The rule is applied to generate a selection list comprising a proper subset of the starting list.