Affluent Americans need not apply. That's what some of the world's largest wealth management firms are saying 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 US 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 US citizens living abroad. Known as Fatca, it requires financial institutions based outside the US to obtain and report information about income and interest payments added to the accounts of American clients.