Bialik and Rauch, who both joined the CBS sitcom in Season 3, were renegotiating their contracts when their co-stars reportedly made the offer. Galecki, Parsons, Cuoco, Helberg and Nayyar are rumored to make $1 million per episode.
The extra $500,000 per episode would bump Bialik and Rauch from $200,000 to nearly $450,000 per episode in the show's prospective 11th and 12th seasons. The series is in its 10th season, and has yet to be renewed.
Deadline had reported last week that Parsons, Galecki, Cuoco, Helberg and Nayyar were in the process of finalizing new two-year contracts. Sources said at the time that Bialik and Rauch were "primed for a major salary bump."
"We are in negotiations," CBS Entertainment president Glenn Geller said in January. "These are going to be, I think, the normal tough negotiations when you're in a situation like this but we are guardedly optimistic."
The Big Bang Theory stars Bialik and Rauch as Amy Farrah Fowler and Bernadette Rostenkowski-Wolowitz, respectively. The sitcom airs Thursdays at 8 p.m. ET.