* Annual donations to Gates, family foundations
* Buffett donating 99 percent of wealth (Adds additional donations)
NEW YORK, July 7 (Reuters) - Investor Warren Buffett has donated another $1.78 billion to several charities, with the bulk going to the Bill & Melinda Gates Foundation, as part of his plan begun in 2006 to donate 99 percent of his wealth.
According to a filing with the U.S. Securities and Exchange Commission, Buffett donated about 23.31 million Class B shares of his insurance and investment company Berkshire Hathaway Inc (BRKa.N) (BRKb.N), with 19.34 million going to the Gates Foundation.
Buffett, 80, also donated smaller sums to four family charities. These include the Susan Thompson Buffett Foundation, named for Buffett's late first wife, and foundations for their children Howard, Peter and Susan. Buffett remarried in 2006.
The shares were donated on Wednesday, the filing shows, when the B shares closed at $76.52. On Thursday, those shares closed up $1.25 at $77.77, while Berkshire Class A shares rose $1,840 to $116,640.
Buffett has to date donated more than $11 billion of Berkshire shares.
Bill Gates, the co-founder of Microsoft Corp (MSFT.O) and a Berkshire director, and his wife, Melinda, created the Gates Foundation to address education, health and poverty problems.
The foundation said it employs 927 people, spent $2.6 billion last year, and has a $37.1 billion endowment. Buffett expects the foundation to spend his gifts, which have totaled roughly $9.5 billion.
In March, Forbes magazine said Buffett is the world's third-richest person, with a $50 billion net worth.
The number of shares that Buffett donates declines by 5 percent each year.
His donations totaled $1.93 billion in 2006, $2.13 billion in 2007, $2.17 billion in 2008, $1.51 billion in 2009 and $1.93 billion in 2010, according to other SEC filings and Berkshire's closing stock prices on the dates the donations were made. [ID:nN02240106] (Reporting by Jonathan Stempel; editing by Andre Grenon, Gary Hill)