Iowa Code § 421A.2: Disclosure prohibited.

A person who obtains any information in the course of or arising out of the business of preparing or assisting in the preparation of a tax return of another person, shall not disclose any of the information obtained unless the disclosure is within any of the following:

1. Consented to in writing by the taxpayer in a separate document.

2. Expressly authorized by state or federal law.

3. Necessary to the preparation of the return.

4. Pursuant to court order.