SAO PAULO, March 28 (Reuters) - Qatar Holdings LLC has put as many as 80 million units of Banco Santander Brasil SA SANB11.SA up for sale, liquidating 40 percent of its position after shares have more than doubled over the past year.

In a Tuesday securities filing, Santander Brasil, the No. 3 private-sector bank, said the offering of units will be underwritten by its investment banking unit as well as Bank of America Corp BAC.N and Credit Suisse Group AG CSGN.S .

Santander Brasil units correspond to a blend of one common and one preferred share in the bank, a division of Spain's Banco Santander SA SAN.MC .

At current prices, the offering could raise as much as 2.8 billion reais ($896 million) for Qatar Holdings, an investment firm controlled by the Gulf state's government, if it chooses to exercise an additional allotment of 12 million units.

Qatar Holdings, an investor in Santander Brasil for nearly seven years, said it expects to remain the second largest shareholder of Santander Brasil after the sale. In an emailed statement, Qatar Holdings said it intends to sell approximately 40 percent of its 5.5 percent stake in Santander Brasil.

The sale, known as a public offering with restricted efforts, differs from standard equity offerings in that Qatar Holdings does not have to request registration of the plan with securities industry watchdog CVM. Only qualified investors can participate, and the deals cannot be marketed through road shows or the media.

The offering follows a 95 percent increase in the price of Santander Brasil units in 2016, a rally that has puzzled many investors.

The units have risen 8.2 percent this year, lagging the 12.8 percent advance of an index tracking shares of banks and financial companies on the S?o Paulo Stock Exchange .IFNC . ($1 = 3.13 reais)

(Reporting by Bruno Federowski and Guillermo Parra-Bernal; Editing by Jeffrey Benkoe) ((Bruno.Federowski@thomsonreuters.com; 55 11 5644 7768; Reuters Messaging: bruno.federowski.thomsonreuters.com@reuters.net))