Quick Read Maxing a Roth 401(k) in the 24% bracket only to withdraw in a 12% or 22% retirement bracket means pre-paying taxes at your highest-ever rate. For married couples, Social Security provisional income between $32,000 and $44,000 can make up to 85% of benefits taxable, and RMDs from large traditional accounts only worsen the problem. Keeping both pretax and Roth accounts lets retirees do conversions at tax rates between 12% and 22% during low-income gap years between retirement and RMDs, wh ...