Despite brand new tax rate reductions belonging to the Jobs and Growth Tax Relief Reconciliation Act of 2003, the top marginal income tax bracket for many retirees can be a whopping fouthy-six.3%. Why? Because Social Security benefits are subject to income tax. Those affected are Social Security recipients who hold the good fortune (misfortune?) to get subject to both the 25% taxes bracket and also the 85% inclusion rate for Social Security benefits. Three Year Rule - The taxes owed in qu...