Most people think about Bitcoin taxes in terms of the capital gains tax they owe on their return. But for people on Medicare, or a few years away from it, a large Bitcoin sale can have a second, less obvious cost: higher Medicare premiums. This surcharge is often called IRMAA, short for the Income-Related Monthly Adjustment Amount.

What IRMAA is

Most Medicare beneficiaries pay a standard monthly premium for Part B (medical insurance) and their plan’s premium for Part D (prescription drug coverage). People whose income is above certain thresholds pay more. That extra amount is IRMAA. It is added on top of the standard Part B premium and on top of the Part D plan premium, and the amount steps up in tiers as income rises.

The Social Security Administration decides whether IRMAA applies, using income information from your federal tax return. The thresholds and surcharge amounts are adjusted from year to year, so it is worth checking the current figures on Medicare.gov or SSA.gov rather than relying on numbers you saw in the past.

Why Bitcoin gains matter

IRMAA is generally based on your modified adjusted gross income (MAGI), which for this purpose is your adjusted gross income plus certain items such as tax-exempt interest. Capital gains are part of adjusted gross income. So when you sell Bitcoin at a gain, trade it for another crypto asset, or spend it on a large purchase, that gain can push your income up for the year. (See Bitcoin Is Property for Tax Purposes and Selling Bitcoin to Buy a House or Car?)

This is true even when the gain is long-term and taxed at a favorable rate, or even at 0%. A long-term gain that costs little or nothing in federal income tax still counts toward the income figure used for IRMAA. (See Could Your Bitcoin Gains Be Taxed at 0%?)

Other Bitcoin income counts too. Mining income, staking rewards, and Bitcoin received as pay are generally ordinary income that raises adjusted gross income. (See Bitcoin Staking Rewards.)

The two-year lookback

The part that surprises many people is timing. IRMAA for a given year is generally based on the tax return from two years earlier. In general terms, a large Bitcoin gain you report for one year can raise your Medicare premiums two years later.

That has a few practical consequences:

• It can affect people who are not on Medicare yet. Someone who sells a lot of Bitcoin a year or two before enrolling may find their first Medicare premiums are higher than expected.
• A one-time sale usually means a one-time bump. Because IRMAA is redetermined each year, a single large sale typically affects the premiums tied to that one tax year, not every year afterward.
• Thresholds are cliffs. Going just one dollar over a tier boundary can move you into the next surcharge level, so the size and timing of a sale can matter.

A simple example

Suppose a retired married couple normally has income comfortably below the first IRMAA threshold. One year they sell Bitcoin they bought long ago and realize a large long-term gain. Their federal income tax on the gain may be modest, but their MAGI for that year jumps well above the threshold. Two years later, each spouse may pay a higher Part B premium and a Part D surcharge for that year. If their income returns to normal the following year, their premiums would generally drop back as well.

Planning ideas to discuss with an advisor

• Spread sales across tax years. Selling in smaller pieces over several years may keep income under a threshold, though it also means more exposure to price swings.
• Use losses where they exist. Realized capital losses can offset gains and reduce income. (See Bitcoin Capital Losses.)
• Choose which units you sell. Selling higher-basis units first can reduce the gain on a given sale. (See Specific Identification Basics.)
• Consider charitable giving. Donating long-held Bitcoin directly to a qualified charity generally avoids recognizing the gain, which also keeps it out of income. (See Donating Bitcoin to Charity.)
• Know about life-changing events. If your income drops because of certain events, such as retirement or the loss of a spouse, SSA allows you to ask for IRMAA to be reconsidered using more recent income. A one-time investment gain by itself is generally not one of those events.

The bottom line

A Bitcoin sale’s true cost is not always limited to the tax on your return. For people on Medicare or approaching it, a large gain can raise premiums two years down the road. Looking at the timing and size of sales ahead of time, ideally with a CPA who understands both digital assets and retirement planning, can help you avoid an unpleasant surprise.

This article is general information about U.S. federal tax and Medicare concepts and is not tax, legal, accounting or benefits advice. Rules, thresholds and premium amounts change, and your situation may differ. Please consult a qualified professional before making decisions.