Barnes & Noble chairman Len Riggio sold 2 million of his shares in the bookstore chain on Tuesday for $13.81 a share, according to an SEC filing this morning. The sale, which generated about $27.6 million, lowered Riggio’s stake in the company to 26.3%, keeping him B&N’s largest shareholder.

The filing said the sale was made for “tax planning purposes.” In addition to the sale, Riggio donated 160,000 shares to The Riggio Foundation, leaving him with about 15.7 million shares.