To help clients evaluate tax-advantaged strategies, it helps to have an understanding of their marginal income tax rates. Under our progressive tax system, this is defined as the highest effective tax rate assessed on the last dollar of income earned.

But for one type of client – a high-income retired person – it keeps getting tougher to identify marginal income tax rates. If you haven't yet reached this conclusion, it isn't necessarily your fault, because a confusing assortment of marginal rates applies only to high-income retired people.

Now, the mood of high-income retired people (and pre-retirees) is changing with the economic cycle and political environment. The ability of such people to plan for secure retirements is clouded by worries that their income taxes could go even higher, in even more complex ways.