The State Bar of California is investigating porn star Stormy Daniels’ lawyer Michael Avenatti, Fox News has confirmed, after a complaint was filed regarding allegedly unpaid taxes.

Fox News on Wednesday obtained an April 18-dated letter verifying the existence of the investigation—unrelated to his representation of Daniels.

“The complaint against attorney Michael J. Avenatti has been reviewed and forwarded to the Enforcement Unit for further investigation and prosecution, if warranted,” said the letter from the state bar, written by Supervising Attorney Anand Kumar and reviewed by Fox News.