1. A computer-implemented method of automatic data determination, the method comprising: receiving a value that a user enters under guidance of a graphical user interface for association with a field of a document; determining, using the received value, a value to be automatically associated with at least another field of the document; and storing, in one or more fields of the document associated with the at least another input field, information indicating (i) the value received in the input field, and (ii) a rule used in determining the value for the at least another input field.