Four Texas residents have been indicted on federal conspiracy and tax charges for promoting an illegal tax shelter scheme that hid more than $1. 5 billion in income and caused an estimated tax loss of over $200 million, federal officials announced Friday.

What we know: A federal grand jury in Dallas returned the indictment on Sept. 22 against Duncan John MacDonald, Sarah Duren, Richard Ronald Cayce, and Thomas Weickgenant, according to U.S. Attorney for the Northern District of Texas Ryan Raybould.

Prosecutors allege the defendants sold clients a fraudulent trust scheme for fees that often exceeded $100,000.