Tata Consultancy Services Ltd. has acquired an Indian business process outsourcing unit from Citigroup Inc.

The $512 million deal for Citigroup Global Services Ltd., announced in October, closed Dec. 31, Citigroup Inc. said. Tata agreed to provide the New York company with technology development, help desk support, and other outsourcing services for nine and a half years.

Citi has taken several steps in recent months to reduce operating expenses. Last month it said it would sell another Indian unit, Citi Technology Services Ltd., to the Bangalore outsourcer Wipro Ltd. for $127 million in cash. Selling Citigroup Global Services reduced Citi's head count by 12,000.