Wis. Stat. § 442.13: Ownership of accountant’s working papers.

All statements, records, schedules, working papers, and memoranda made by a certified public accountant incident to or in the course of professional service to clients by a certified public accountant, except reports submitted by a certified public accountant to a client, shall be and remain the property of the certified public accountant, in the absence of an express agreement between the certified public accountant and the client to the contrary. No such statement, record, schedule, working paper, or memorandum shall be sold, transferred, or bequeathed, without the consent of the client or the client’s personal representative or assignee, to anyone other than any member of the firm of the certified public accountant.