It’s very rare that banks turn away money, but that’s exactly what some of the world’s largest banks are doing. Some of the world’s largest wealth management firms are turning away American millionaires in anticipation of Washington’s implementation of the Foreign Account Tax Compliance Act, which seeks to prevent tax evasion by Americans with offshore accounts. HSBC Holdings, Deutsche Bank, Bank of Singapore, and DBS Group Holdings all say they have turned away business from U.S. clients.

The 2010 law, to be phased in starting on Jan. 1, 2013, will mean additional compliance costs for banks and fewer investment options for U.S. citizens living abroad. Known as Fatca, it requires financial institutions based outside the U.S. to obtain and report information about income and interest payments added to the accounts of American clients. The Internal Revenue Service held

Bank of Singapore, the private-banking arm of Oversea-Chinese Banking Corp., has declined to accept millions of dollars from Americans because it doesn’t want to deal with the regulatory hassle, according to Chief Executive Officer Renato de Guzman. “It’s too complex, too challenging,” he says. “You probably should have a dedicated team to handle them or to understand what can be done or what cannot be done.”

Some U.S. citizens are sidestepping the new tax reporting concerns – and possibly saving money by renouncing their citizenship. A record 1,780 gave up their U.S. passports last year, compared with 235 in 2008, according to the IRS. One of them was Eduardo Saverin, the billionaire co-founder of Facebook. The move may reduce his tax bill as Facebook completes an initial public offering that values the social network at more than $100 billion. Brazilian-born Saverin is a resident of Singapore.

If Americans choose to bank with a non-U.S. firm such as HSBC, their investment choices are limited. At the HSBC branch in the bank’s Asia regional headquarters in Hong Kong, Americans can only make savings deposits. HSBC decided last July that it would no longer offer wealth management services to Americans from locations outside their home country after tax authorities stepped up a probe of the London-based bank’s U.S. clients. Americans would be “better served” by private bankers in the U.S., Goh Kong Aik, a spokesman for the firm in Singapore said.

The growth in wealth in Asia makes it easier for banks to refuse Americans. Asia has the world’s ­fastest-growing number of people with more than $1 million in investable assets, according to a report last year by Bank of America and Capgemini, a management consultant. The number of millionaires in Asia climbed 9.7 percent in 2010, to 3.3 million, higher than the 8.6 percent growth in North America. The combined wealth of Asian millionaires increased to $10.8 trillion, topping Europe for the first time.