Converting a portion of an IRA to a Roth IRA is complex process that involves many moving parts and can have some unintended consequences if not properly handled, including a possible impact on Medicare premiums two years after the conversion.
To help make this easier, there is the “Will My Roth IRA Conversion Be Penalty Free" flowchart. It addresses common issues that occur when doing a Roth conversion:
Implications for IRAs with nondeductible IRA contributions
Pro-rata and aggregation rules
Simple IRA rules
Medicare Part B and Part D surcharge impact
5 year rule on the Roth IRA
5 year rule on the conversion
RMD coordination issues
Updated 2019