Last spring a new client sat across from me holding a letter from Social Security. Her Medicare premium had nearly doubled, and she hadn't changed a thing.

What changed was her income from two years earlier. That was the year she sold her practice.

The surcharge has a name, IRMAA, and it catches a lot of retiring attorneys off guard. Let's walk through how it works and a few ways you may want to plan around it.

First, the part that surprises people most. Medicare looks back two years when it sets your premium, so the decisions you make while you're still working can follow you into retirement.