When is a workfile required for an appraisal according to USPAP?

A workfile is specifically required under USPAP when developing an opinion of value. This requirement ensures that all pertinent data, analyses, and conclusions made during the appraisal process are documented and can be substantiated. The workfile must include materials necessary to support the appraisal, including any data key to forming the opinion of value.

In the context of the options provided, relying solely on raw Automated Valuation Model (AVM) output does not constitute full appraisal development, as it may lack the contextual analysis or additional data needed to arrive at a credible opinion of value. Thus, while raw AVM output might be a component of a workfile, it does not drive the necessity for a workfile. The essence of USPAP emphasizes thoroughness in the appraisal process, and this is captured by the requirement for workfiles during the development of an opinion of value.

A workfile is not required merely when modifications are made to an appraisal or always for all appraisals, but specifically during the appraisal development process where critical analyses and decisions are documented.