Barkin received the papers Thursday at the couple's New York mansion, sources told the New York Post.
"She's shocked," a source told the newspaper. "She wasn't expecting it."
A prenuptial agreement grants Barkin $20 million in case of divorce but the figure rises dramatically after a predetermined date, which apparently is approaching, the source said.
Perelman, 62, is worth an estimated $6 billion, the Post said.
He met Barkin, 51, at a post-Oscar party in 1999. They briefly split in 2004 but have been together non-stop since.
Barkin is Perelman's fourth wife and he has six children. She has two teenage children with her ex-husband, actor Gabriel Byrne.