In addition, he could be paid up to Â£2.1 million this year in salary and bonus if he hits his targets.
His annual salary at Edinburgh-based RBS is Â£700,000 and the bank is due to make a payment of Â£1.2 million in cash on February 19th to the new finance director, followed by a further payment of restricted stock in four payments up to February 2010.
Mr Whittaker will also receive Â£1 million of RBS shares as compensation for Citigroup options and stock awards he forfeited when he resigned and three annual tranches of restricted shares by February 2009.
In addition to Â£4.5 million worth of cash and shares over four years and an annual salary of Â£700,000, the RBS finance director could earn cash bonuses each year of as much as 200 per cent of his salary.
Mr Whittaker is leaving the company at which he has spent most of his professional life for RBS at a point of rapid expansion of the bank. The UK's banking giants have started to look across to the US for executives in recent years.