Warren Buffett's Berkshire Hathaway spent $1.2bn (£971.5m) today to buy back shares from the estate of an unnamed investor.
The conglomerate also raised the threshold for future buybacks, in a move that was read as indicating a greater willingness by Mr Buffet to support the company's share price.
Berkshire said it would raise the threshold to 120 per cent of book value from 110 per cent.
Meanwhile, the seller in today's buyback may have been spurred on to offload stock ahead of the deadline for the "fiscal cliff".
Congress and the White House are currently debating ways to put off the automatic tax rises and spending cuts that kick in at the beginning of next year, but most watchers expect a hike in estate taxes.