1. A computer-implemented method, comprising: receiving first user input that: i) creates a beginning test node for a computer-executable decision tree, the computer-executable decision tree being executable by a computing system for use in determining taxes for a particular commercial transaction, ii) defines a comparison field for the beginning test node, wherein the comparison field for the beginning test node specifies a first particular field that is in either an input document or a calling computer system and that is to provide a first particular value arising from the particular commercial transaction, and iii) defines a list of allowed values for the first particular value arising from the particular commercial transaction; generating, in response to receiving the first user input, a first graphical user interface to present a first graphical view of the decision tree, the first graphical view of the decision tree including: (a) the beginning test node, (b) a yes answer node of the beginning test node, and (c) a no answer node of the beginning test node; receiving second user input that: i) creates a second test node for the decision tree by selecting the yes answer node of the beginning test node, which second test node is dependent upon the beginning test node, ii) defines a second comparison field for the second test node, wherein the second comparison field for the second test node specifies a second particular field that is in the input document or the calling computer system and that is to provide a second particular value arising from the tax determination process, and iii) defines a list of allowed values for the second particular value arising from the particular commercial transaction; generating, in response to receiving the second user input, a second graphical user interface to present a second graphical view of the decision tree, the second graphical view including: (a) the beginning test node, (b) the yes answer node of the beginning test node, (c) the no answer node of the beginning test node, (d) the second test node that is dependent on the beginning test node, (e) a yes answer node of the second test node, and (f) a no answer node of the second test node; receiving third user input that creates a third test node for the decision tree by selecting the no answer node of the beginning test node, which third test node is dependent upon the beginning test node; and executing, by the computing system, the decision tree in order to determine taxes for the particular commercial transaction, wherein the computing system is configured to, during execution of the decision tree: i) proceed from the beginning test node to the second test node as a result of a positive result in a comparison action between the first particular value and the list of allowed values for the first particular value, and ii) proceed from the beginning test node to the third test node as a result of a negative result in the comparison action between the first particular value and the list of allowed values for the first particular value.