Meet Margaret

Margaret, 63. Registered nurse who retired last year after a 35-year career, living off a taxable brokerage account and cash savings.

She has $1,400,000 in a traditional 401(k) and hasn't claimed Social Security yet. Gross income right now is about $20,000 per year, which is below the $30,000 standard deduction for married couples, so taxable income is $0. Those early years have the entire 10% and 12% federal bracket available for Roth conversions. At 73, required minimum distributions on a balance that may exceed $2.7 million will force six-figure taxable income whether she needs it or not. She has 10 years to act.