What Is MAGI and Why It Matters for Your Taxes
AGI vs. MAGI: Why There Are Two Numbers
When you file your federal tax return, you calculate your Adjusted Gross Income (AGI) — your total income minus specific above-the-line deductions like 401(k) contributions, HSA contributions, and student loan interest. AGI is what determines your tax bracket after subtracting the standard or itemized deduction.
But AGI isn't the last word. Congress created Modified Adjusted Gross Income (MAGI) to determine eligibility for specific tax benefits — and it adds certain deductions back to your AGI, effectively making your income look higher for those particular purposes.
MAGI is not a single number. Different tax benefits use different MAGI formulas — adding back different items depending on the rule in question. Your Roth IRA MAGI, your ACA MAGI, and your Medicare MAGI may all be different figures derived from the same tax return.
Use the MAGI Calculator to calculate your MAGI for each major purpose automatically.
The Common MAGI Add-Backs
Most MAGI calculations start with AGI and add back some or all of the following:
Student loan interest deduction: Up to $2,500 in student loan interest is deductible above-the-line. For Roth IRA and IRA deductibility calculations, this deduction is added back.
Traditional IRA deduction: If you deducted contributions to a traditional IRA, that amount is added back for Roth IRA eligibility calculations. This prevents IRA contributors from artificially reducing their MAGI.
Passive activity losses: Rental real estate and other passive losses that were deductible on your return may be added back for certain MAGI calculations.
Tuition and fees deduction: This deduction, when available, is added back for MAGI-dependent benefits.
Foreign earned income exclusion: US citizens living abroad can exclude foreign earned income from taxable income, but it's added back to MAGI for most benefit calculations.
Tax-exempt Social Security benefits: The portion of Social Security not included in your taxable income is added to MAGI for ACA and Medicare calculations.
Tax-exempt interest income: Municipal bond interest, which is excluded from federal income tax, is added to MAGI for Medicare IRMAA calculations.
Why Different Rules Use Different Formulas
Congress designed each provision independently, which is why there's no single universal MAGI formula. Here's how the three most important MAGI calculations differ:
| Purpose | Key Add-Backs |
|---|---|
| Roth IRA eligibility | Student loan interest, IRA deduction, tuition, foreign income exclusion |
| ACA premium tax credit | Tax-exempt SS benefits, tax-exempt interest |
| Medicare IRMAA | Tax-exempt interest only |
The practical implication: you may be under the Roth IRA phase-out limit but still face IRMAA surcharges, or vice versa. Each one requires a separate calculation.
Roth IRA MAGI Limits and the Phase-Out
Direct Roth IRA contributions are limited based on your MAGI. In 2026:
- Single filers: Phase-out begins at $150,000, contribution is zero above $165,000
- Married filing jointly: Phase-out begins at $236,000, contribution is zero above $246,000
- Married filing separately: Phase-out begins at $0, effectively $0 allowed above $10,000
Within the phase-out range, your maximum contribution is reduced proportionally. The calculation:
Reduced contribution = $7,000 × (1 − (MAGI − Phase-out start) / Phase-out range)
Example: Single filer with $157,500 MAGI. The phase-out range is $15,000. Your MAGI is $7,500 into the range — halfway through. Your maximum Roth contribution is half of $7,000 = $3,500.
The Backdoor Roth IRA
If your MAGI exceeds the Roth contribution limit, the backdoor Roth strategy lets you still get money into a Roth:
- Contribute to a non-deductible traditional IRA (no income limit on contributions)
- Convert the traditional IRA to a Roth IRA
The conversion is generally tax-free if you have no other pre-tax IRA balances. See the Backdoor Roth Calculator to check if this strategy works for your situation.
ACA Premium Tax Credits and the Subsidy Cliff
The Affordable Care Act provides premium subsidies for health insurance purchased on the marketplace, based on your household MAGI as a percentage of the Federal Poverty Level (FPL).
Approximate 2026 subsidy thresholds:
| Household Size | 400% FPL (Subsidy Cliff) |
|---|---|
| 1 person | ~$60,240 |
| 2 people | ~$81,760 |
| 3 people | ~$103,280 |
| 4 people | ~$124,800 |
The ACA subsidy "cliff" at 400% FPL is severe: crossing the threshold by even $1 can eliminate thousands of dollars in annual premium subsidies. For early retirees or self-employed individuals managing their taxable income, staying below 400% FPL is often worth significant planning effort.
Strategies to stay below the ACA cliff:
- Maximize traditional 401(k) or IRA contributions to reduce MAGI
- Contribute to an HSA
- Time Roth conversions carefully to avoid pushing MAGI over the threshold
- Use tax-loss harvesting to offset capital gains
ACA MAGI formula: AGI + tax-exempt Social Security benefits + tax-exempt interest income. It does not add back student loan interest or IRA deductions, making it simpler than other MAGI calculations.
Medicare IRMAA: The Two-Year Lookback
If your MAGI exceeds certain thresholds, you pay higher Medicare Part B and Part D premiums through the Income-Related Monthly Adjustment Amount (IRMAA). For 2026 premiums, Medicare looks at your 2024 MAGI.
This two-year lookback creates a planning challenge: high income in one year means higher Medicare costs two years later. Common triggers include large Roth conversions, business sales, or required minimum distributions.
2026 Part B IRMAA thresholds (based on 2024 income):
| 2024 MAGI Single | 2024 MAGI Married | Extra Monthly Cost |
|---|---|---|
| ≤ $106,000 | ≤ $212,000 | $0 |
| $106,001 – $133,000 | $212,001 – $266,000 | +$70.00 |
| $133,001 – $167,000 | $266,001 – $334,000 | +$176.60 |
| $167,001 – $200,000 | $334,001 – $400,000 | +$283.20 |
| $200,001 – $500,000 | $400,001 – $750,000 | +$389.80 |
| Over $500,000 | Over $750,000 | +$426.10 |
You can appeal an IRMAA surcharge if your income has since decreased due to a life-changing event (retirement, divorce, death of spouse) using Form SSA-44.
Medicare MAGI formula: AGI + tax-exempt interest income. Social Security benefits are not added back for Medicare IRMAA — unlike the ACA calculation.
Strategies to Reduce Your MAGI
Maximize Pre-Tax Retirement Contributions
Every dollar contributed to a traditional 401(k) or 403(b) reduces your W-2 income, which lowers your AGI and MAGI. The 2026 contribution limit is $23,500 ($31,000 if age 50+).
Impact example: A married couple earning $250,000 combined who each max out a 401(k) reduces MAGI by $47,000 — potentially keeping them in a lower Roth phase-out tier, below IRMAA thresholds, and preserving ACA eligibility.
Contribute to an HSA
Health Savings Account contributions are above-the-line deductions. For 2026: $4,300 (self-only) or $8,550 (family). The deduction reduces your AGI and MAGI dollar-for-dollar.
Harvest Capital Losses
Capital losses offset capital gains on your return. Net losses reduce your AGI (up to $3,000 of ordinary income per year, with excess carried forward). This directly reduces MAGI.
Defer or Accelerate Income
If you're near a MAGI threshold that triggers a cliff (ACA subsidy, Roth phase-out, IRMAA), timing income carefully around year-end can help. Deferring a year-end bonus into January, or accelerating retirement plan distributions into this year, are common levers.
Roth Conversion Laddering
Strategic Roth conversions let you control your MAGI in retirement. Converting just enough each year to fill lower brackets — while staying below IRMAA thresholds or the ACA cliff — is a core retirement income planning strategy. Model this with our Roth Conversion Calculator.
Putting It All Together
MAGI is not one number — it's a framework for understanding how your income interacts with the tax code. The same income on your tax return can look different for Roth IRA purposes versus Medicare versus the ACA.
The good news: every add-back to MAGI starts with your AGI. The best way to reduce MAGI across the board is to lower your AGI through pre-tax retirement savings, HSA contributions, and strategic income timing.
Related tools: MAGI Calculator | Roth Conversion Calculator | Backdoor Roth Calculator