The British bank, which is 84-percent owned by the government after a series of enormous bailouts, was "not going to pay a penny more than we need to," chief executive Stephen Hester told a panel of lawmakers. "It is my duty as chief executive to protect shareholder interests and pay the minimum bonuses that our group can get away with - consistent with motivating and keeping good staff," Hester told the Treasury Select Committee.
He added that the bonus levels would be minimal when they are announced in late February.
RBS was undone by the global credit crunch and its take-over of Dutch banking giant ABN Amro at the top of the market in 2007 just before the financial crisis ravaged markets and economies across the world.
Some observers blame the banking sector's bonus culture for encouraging excessive risk-taking and helping to tip the world economy into recession.
Britain spent billions of pounds bailing out some of the country's biggest institutions including RBS and Lloyds Banking Group - which is 43 percent owned by the state - while lender Northern Rock was nationalised.
Last month, the government slapped a 50-percent tax rate on bank employee bonuses above 25,000 pounds (28,000 euros, 40,400 dollars) to recoup some of the cash spent rescuing the financial sector.
Britain hopes to recoup more than half a billion pounds - but recent media reports have suggested that some large financial institutions may be considering moving staff to avoid the so-called "super tax."