A method and system generate customized financial document templates in a document preparation system, according to one embodiment. The method and system receive document data from a user corresponding to a document including a plurality of custom data fields in a custom template. The method and system map the custom data fields to system data fields from a relatively small subset of data fields selected from a system data field pool based on the characteristics of the user. The method and system generate a custom form template based on the document data and the mapping of the custom data fields to system data fields.