French Magazine Le Point says the Wildenstein family is being asked to pay €600m in back taxes:

In its edition to be published Thursday, the weekly says that a series of adjustment notices were issued to the heirs of Mr. Wildenstein for €600 million, excluding penalties, of which 250 million are claimed to Guy Wildenstein, the eldest son of art dealer who died in 2001.

“There is a tax adjustment to the persons entitled to family tax”, told AFP a source familiar with the matter.

For its part, the Budget Ministry has declined to comment, citing tax secrecy. Guy Wildenstein’s lawyers were not immediately available.

A judicial inquiry was opened in 2011 by the Paris prosecutor’s office following a complaint of tax fraud filed by the Department of Budget against Guy Wildenstein.

600 million euros in back taxes for the heirs of art dealer Wildenstein (Le Point)