An anonymous bidder has agreed to pay a record $US4,567,888 million ($6.6 million) at an annual charity auction to have a private lunch with Warren Buffett, the billionaire chairman of Berkshire Hathaway Inc.

The winning bid, which was submitted during a five-day online auction on eBay that ended Friday night, was nearly one-third higher than the previous record $US3.4 million ($4.9 million) in both the 2012 and 2016 auctions.

Proceeds benefit the Glide Foundation, a charity in San Francisco’s Tenderloin district that serves the poor, homeless or those battling substance abuse.

Mr Buffett, 88, has raised about $US34.2 million ($49.3 million) for Glide in 20 annual auctions, which began in 2000 and moved to eBay in 2003.

The winning bidder and up to seven friends can dine at the Smith & Wollensky steakhouse in Manhattan with Mr Buffett, who says he will discuss anything apart from his next investments.

This year’s auction drew 18 bids from five bidders.