Are Ghost Taxes Creeping Into Your DexCom Retirement Plan?

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'Many DexCom employees underestimate how much “ghost taxes” can erode retirement income. Understanding these hidden thresholds today can help you make more thoughtful decisions for tomorrow’s financial well-being,' — Michael Corgiat, a representative of The Retirement Group, a division of Wealth Enhancement.

'Many DexCom employees are surprised by how quickly hidden taxes like AMT, NIIT, and IRMAA can reduce retirement income, making it important for retirees to stay informed and thoughtfully plan so these costs don’t catch them off guard.' — Brent Wolf, a representative of The Retirement Group, a division of Wealth Enhancement.

In this article, we will discuss:

1. The five “ghost taxes” that may unexpectedly impact retirement income.

2. How these taxes can affect DexCom employees and retirees.

3. Strategies to better understand and prepare for these tax implications.

How DexCom Employees Can Prepare for the Five “Ghost Taxes” That Could Haunt Retirement

There are several lesser-known surcharges and thresholds that may unexpectedly increase your tax bill in retirement, even if you already understand federal, state, and local tax obligations. These include the Alternative Minimum Tax (AMT), the Net Investment Income Tax (NIIT), the Medicare Income-Related Monthly Adjustment Amount (IRMAA), the Social Security “tax torpedo,” and the new senior deduction. Because many of these thresholds are not adjusted for inflation, they increasingly impact retirees, including those from DexCom.

1. AMT: Alternative Minimum Tax

The AMT is a parallel tax system designed to make sure higher-income individuals pay at least a minimum amount of taxes. It has its own tax brackets, forms, and rules, with a top rate of 28%. ¹  Some deductions available under the traditional tax system are limited under AMT rules.

For 2025, the AMT exemptions are:

• - $88,100 for single filers (phasing out at $626,350)

• - $137,000 for married couples filing jointly (phasing out at $1,252,700)

High income, exercising incentive stock options, large capital gains, or numerous itemized deductions may trigger AMT. Even though long-term capital gains receive preferential tax treatment, they can still reduce your AMT exemption. If AMT is paid in one year, a tax credit may be available in future years when AMT is not owed.

2. NIIT: Net Investment Income Tax

The NIIT applies a 3.8% tax on net investment income when modified adjusted gross income (MAGI) exceeds:

• - $200,000 for single filers

• - $250,000 for married couples filing jointly ²

This tax applies to dividends, interest, rental income, gains from home sales, and capital gains beyond exclusion limits. Withdrawals from 401(k)s and traditional IRAs are not directly taxed by NIIT, but they may increase MAGI and cause other investment income to be taxed.

Strategies to limit exposure include contributing to traditional retirement accounts, using health savings accounts (HSAs), and tax-loss harvesting. For instance, tax-loss harvesting allows you to use up to $3,000 in capital losses annually to offset ordinary income. ³  

For individuals age 70½ or older looking to reduce MAGI, qualified charitable distributions (QCDs) may help. QCDs allow you to donate to qualified charities on a tax-free basis directly from your IRA, satisfying required minimum distribution (RMD) rules without bringing distributions into income. In 2025, up to $108,000 may be donated tax-free. ⁴

3. IRMAA: Income-Related Monthly Adjustment Amount

IRMAA adds a surcharge to Medicare Parts B and D premiums for higher-income retirees and is based on MAGI from two years prior.

For 2025, IRMAA applies when MAGI exceeds:

• - $106,000 for single filers

• - $212,000 for married couples filing jointly

Even a small increase above these limits can place retirees in a higher premium bracket. Tax-exempt interest from municipal bonds is included in MAGI for IRMAA purposes. Premiums and IRMAA can be deducted from Social Security payments or paid directly. Social Security allows individuals experiencing major life changes, such as retirement or death of a spouse, to request revised IRMAA calculations.

4. The Social Security “Tax Torpedo”

Social Security benefits may be taxable depending on “provisional income,” which includes:

• - Adjusted gross income

• - Non-taxable interest

• - One-half of Social Security benefits

If provisional income exceeds:

• - $34,000 for single filers

• - $44,000 for married couples filing jointly

...then up to 85% of Social Security benefits may be taxable. ⁵

Delaying Social Security up to age 70 increases benefits by 8% per year beyond full retirement age.

5. The 2025–2028 New Senior Deduction

From 2025 to 2028, individuals age 65 and older may qualify for a new senior deduction:

• - $6,000 for single filers

• - $12,000 for married couples filing jointly

This deduction phases out at:

• - $75,000 MAGI for single filers

• - $150,000 MAGI for joint filers

This is separate from the standard senior deduction, which currently adds $2,000 for individuals or $3,200 for married couples age 65 or older.

Need Help Navigating These Taxes?

Understanding how AMT, NIIT, IRMAA, Social Security rules, and senior deductions affect retirement income can be complex, especially for DexCom retirees managing pensions, 401(k)s, and other investments. The Retirement Group can help you better understand how these tax considerations relate to your retirement planning. Call  (800) 900-5867  for guidance.

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Sources:

1. Tax Foundation. “ 2026 Tax Brackets .” 9 Oct. 2025.

2. Gravelle, Jane G., and Don J. Marples.  The 3.8% Net Investment Income Tax: Overview, Data, and Policy Options .  Congressional Research Service, 30 June 2023, crsreports.congress.gov/product/pdf/R/R41413.

3. IRS. ' Topic no. 409, Capital gains and losses .' 12 Sep. 2025.

4. Wealth Enhancement. ' 7 Tax Moves to Consider Before The End of The Year ,' by Mary Taliaferro, CFP. Nov. 5, 2025. 

5. Investopedia. ' Provisional Taxes: What They Are and How They Work ,' by Julia Kagan. 4 Sep. 2025.