Tax planning is an ever-important, but often neglected, part of financial health. Over the years, taking advantage of seemingly small tax deductions can add up to a tremendous amount of wealth, due to the impact of compound interest. (For an extreme example of this, check out this hypothetical couple who, with careful planning, never paid any income taxes and used that to retire in their 40s.) And the opportunities (and penalties for neglect) don’t go away in your retirement years. In fact, they may only grow in importance, when the right portfolio withdrawal strategy can lower your tax bracket and help you avoid costly, unexpected tax bills.

But even beyond income tax planning — which is complicated enough — there are other areas of your financial life that are also tied to the amount of income you report on your tax return. These ancillary concerns can further complicate the tax planning picture and make focusing on solely on income taxes a case of “not seeing the forest for the trees.”

One such issue involves Medicare part B insurance premiums, a program in which over 50 million Americans are enrolled. Did you know that part B premiums go up if your income exceeds certain levels? For about 7% of retirees on the program, they will get hit by a premium surcharge based on their income, and in some cases, the surcharge increases their total costs dramatically.

Here’s basically how the program works: the level of your income (actually, technically your “Modified Adjusted Gross Income” reported on your tax return) will determine how much of the costs of Medicare’s services are born by you, instead of Uncle Sam. (Please note, the numbers in the following chart are for taxpayers filing “single.” Married filers should double those numbers to figure their costs. Also, these numbers were 2017; we’ll get to the 2018 changes later in this article.)

And now you can see why tax planning is so important, because the Medicare premiums you pay are affected by your MAGI, and some forms of retirement income do not impact MAGI, while others do. Further, planning mistakes that push your MAGI up into the highest bracket is an increase in premiums of over 200%! To put it in dollar terms, that’s about $4,500 per year of increased cost.

This is why having a well-designed retirement income strategy is so important, and one that considers the effects of income to Medicare premiums as well. Take a look at the following chart that shows how Medicare premiums are increasing even more for 2018 and 2019.

Medicare premiums 2017-2019

As you can see, the top tiers have been pushed down, so that more and more retirees are being hit by the higher premiums. And with the current budget deficits facing Congress, that seems unlikely to change.

So, as health care costs continue to rise, it seems clear that Congress will have to shift more costs to seniors, and it’s far more politically palatable to target those with a “high income.” However, as always the “devil is in the details,” and a well-designed withdrawal strategy can help you avoid unnecessary costs. This is just another reason why you might consider hiring a proactive, knowledgeable CFP professional who acts a your “Personal CFO.”