Tax calculations are delaying the bequest of billionaire George Mitchell. The oil tycoon signed the pledge in 2010 and died two years ago. His foundation has yet to receive any funds from the estate pending IRS settlement of the tax return, said Katherine Lorenz, president of the Cynthia & George Mitchell Foundation and the couple’s granddaughter. She declined to elaborate on the specific reason for the delay.

“My grandparents were very public that they were very dedicated to giving the majority of their wealth to charity issues, but I don’t feel at liberty to say how much until the estate settles,” Lorenz said.

Contingent Trusts

The couple gave away $400 million during their lives, according to Lorenz. At the time of his death, Mitchell had a net worth of at least $3 billion, according to data compiled by Bloomberg.

Determining how Harold Simmons’s pledge was met is even harder to ascertain. Simmons built an $8 billion fortune staging leveraged buyouts of Arby’s franchise operators and sugar beet processors in the 1980s. The Texan and his wife Annette joined the Giving Pledge in 2011. The couple gave at least $350 million to charity through 2013, based on foundation tax returns and other public disclosures.

“Though we have made many philanthropic gifts during our lifetimes and plan to do more, we have also established trusts to carry on this giving after my death,” they wrote in their Giving Pledge letter.

In the will he signed three weeks before his death in December 2013, Simmons gave two of his four daughters, Lisa Simmons and Serena Simmons Connelly, assets worth $6 billion through inheriting Contran Corp., a holding company that controls stakes in four public companies worth $4.5 billion and cash from the sale of another company in 2013. Annette Simmons received about $700 million in preferred stock and other assets.

‘Simple Proposition’

The billionaire indicated in his will that two charitable foundations could receive $400 million. Those foundations weren’t funded because their creation was contingent on his heirs not being alive, estate lawyers disclosed during a legal challenge by Bloomberg News on the will’s redaction last year.

The heirs -- Lisa, 60, and Serena, 45 -- run the Harold Simmons Foundation, which disclosed net assets of $56 million in 2013 after accounting for $38 million in refundable loans owed to the late billionaire, according to its tax return. The sisters and Annette Simmons didn’t return e-mails and phone calls seeking comment.