Sources at the banking group told the Financial Times that progress to date in reducing overlaps in its existing IT systems means executives are now targeting savings several times higher than the original estimate.
The technology consolidation is part of a move by chief executive Vikram Pandit to create "a more cohesive company" from Citi's sprawling businesses, the newspaper added.
Citi had originally aimed to save $3 billion over three years by rationalizing its technology division, which has 140,000 employees and some 25,000 software developers.
According to regulatory filings cited by the Financial Times, Citigroup spent $4.9 billion on IT and communication expenses in 2008. Operating costs are believed to add billions more to that figure, it said.
Citibank originally opened for business in 1812.