The winning bidder and up to seven others will eat lunch with Buffett on a date to be agreed at the Smith & Wollensky steakhouse in New York.
Proceeds benefit the Glide Foundation, a nonprofit in San Francisco's Tenderloin district that offers meals, health care, child care, housing and job training for the poor and homeless.
Buffett began donating lunches after his first wife Susan, who died in 2004, introduced him to Glide and its founder, the Rev. Cecil Williams. The 10 prior auctions have raised more than $5.9 million.
This year's auction is being held on eBay Inc's website and closes on Friday at 10:30 p.m. EDT.
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As of 4 p.m. EDT Tuesday, there had been 31 bids for the lunch. Bids typically soar in the final hour or two.
Salida Capital Corp, a Toronto-based wealth management firm, won last year with a $1,680,300 bid. The record bid is $2,110,100 in 2008 by Hong Kong-based investor Zhao Danyang.
Buffett, 79, is worth $47 billion according to Forbes magazine. He built his fortune through Berkshire Hathaway Inc, his Omaha, Nebraska-based insurance and investment company.
In 2006, Buffett pledged most of his wealth to the Bill & Melinda Gates Foundation and four family charities.
