Laura Brook, director of international relations for the Financial Planning Association, points out that advisors should be sure to determine their clients' citizenship status. "Do you ask them if they are American citizens?" she asks. "If not, you may unknowingly be working with some people who are resident aliens. Clients who are not U.S. citizens, or who are married to non-citizens, may have cross-border planning issues that result in serious tax or estate planning problems."