Short answer: For most IRMAA planning, start with AGI + tax-exempt interest. Then add any planned taxable event you are testing, such as Roth conversions, RMDs, IRA withdrawals, capital gains, or taxable home-sale gains.
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Quick checklist
- Usually counts: wages, pension income, interest, dividends, taxable Social Security, RMDs, IRA withdrawals, Roth conversions, taxable capital gains, and taxable home-sale gains.
- Usually added back: tax-exempt interest, including municipal bond interest.
- Usually does not count directly: qualified Roth IRA withdrawals, HSA distributions for qualified medical expenses, and the nontaxable part of Social Security.
- Easy to miss: mutual fund capital-gain distributions, consulting income, severance, and a taxable gain from selling a second home or rental property.
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Sponsor this placementWhat counts because it is in AGI?
AGI already includes many income items people ask about. That is why the checklist starts with AGI instead of rebuilding every line from scratch.
- Traditional IRA withdrawals and RMDs.
- 401(k), 403(b), and pension distributions.
- Roth conversions, because the taxable conversion amount usually raises AGI.
- Taxable capital gains, dividends, interest, wages, consulting income, and taxable Social Security benefits.
What gets added back?
Tax-exempt interest matters for IRMAA even though it may not be taxable for regular income tax. Municipal bond interest is the common example. A retiree with $120,000 of AGI and $6,000 of municipal bond interest would use about $126,000 as the IRMAA planning number before testing other income events.
What should not be double counted?
Do not add an item again if it is already included in AGI. Taxable Social Security is a common example: if the taxable portion is already in AGI, do not add gross Social Security benefits again. Qualified Roth IRA withdrawals are different from Roth conversions; qualified withdrawals usually do not raise AGI.
Before a planned income event
Use the calculator before you lock in a Roth conversion, RMD strategy, taxable IRA withdrawal, capital gain, or home sale. The important question is not only whether IRMAA applies, but how much room remains before the next bracket.
Common planning mistakes
- Using taxable income after deductions instead of AGI.
- Forgetting municipal bond interest because it feels tax-free.
- Adding all Social Security benefits on top of AGI instead of only using the taxable portion already in AGI.
- Assuming qualified Roth IRA withdrawals and Roth conversions work the same way.
- Ignoring the two-year lookback between the income year and premium year.
Next step: compare your number with the 2026 IRMAA brackets, then save the IRMAA planning checklist.