Selling AI Stocks Before Medicare Can Raise Premiums Two Years Later

A large capital gain from selling artificial intelligence stocks in a taxable account can increase Medicare Part B and Part D premiums for beneficiaries two years later, even if the investor has already spent or reinvested the proceeds. This mechanism, driven by the income-related monthly adjustment amount, creates a specific financial trap for investors nearing retirement age who look to reduce portfolio concentration before healthcare coverage begins.

Reuters reported on October 9 that the S&P 500 has risen 117% since its closing low in October 2022, marking the fourth anniversary of the AI-driven bull market. For a hypothetical 64-year-old investor who bought AI stocks early in a taxable brokerage account, this growth may have resulted in a single holding dominating the portfolio. While selling shares to cut risk before Medicare kicks in appears to be prudent risk management, the realized gain impacts federal tax returns in a way that alters future healthcare costs.

The Centers for Medicare & Medicaid Services (CMS) states that income-related surcharges affect roughly 8% of people with Part B. Medicare calculates these surcharges based on modified adjusted gross income, or MAGI, from a federal tax return filed two years prior. MAGI includes adjusted gross income plus tax-exempt interest. Account balances and unrealized paper gains do not factor into this calculation; a holding can grow to $1 million without affecting premiums until it is sold. Once sold, the profit becomes taxable income. Although long-term capital gains may receive lower income tax rates than wages, they still count toward the Medicare surcharge threshold.

Because Medicare sets premiums using data from two years earlier, a large sale made at age 64 determines the premiums paid at age 66. The surcharge applies to both Part B and Part D and is assessed per person. If an investor files jointly, a large gain increases household income on the shared return, potentially causing a spouse on Medicare to face higher premiums as well. The temporal gap between the sale and the premium increase makes it easy for investors to overlook this connection.

Social Security outlines specific life-changing events that allow beneficiaries to request a lower surcharge by filing Form SSA-44. Qualifying events include marriage, divorce, death of a spouse, retirement, or a reduction in work hours. A voluntary stock sale does not qualify as a life-changing event because the subsequent drop in income is a result of the investor's choice rather than an external change in employment status. However, if the investor also retires from work, that cessation of employment is a qualifying event. In such cases, the request for a lower premium relies on the lost paycheck, not the stock sale itself.

Investors still have until December 31 to decide how much gain to report on the current year's tax return. Financial planning should include a comparison between selling all shares at once versus spreading sales over two years. Investors should also account for tax-exempt interest in their Medicare income calculations. Those planning to retire soon should retain documentation from their employer confirming their last day of work, as this evidence supports a Form SSA-44 request for a new determination based on lower income.