Modified Adjusted Gross Income (MAGI): Definition and How It Works

Modified Adjusted Gross Income (MAGI) is Adjusted Gross Income (AGI) with certain deductions and exclusions added back, as specified by the particular tax provision being applied. There is no single, universal MAGI figure — Congress and the IRS define MAGI differently for each provision in the Internal Revenue Code. As a result, a taxpayer may have several different MAGI amounts simultaneously, each calculated for a distinct purpose. CPAs must identify which MAGI definition applies for the provision at issue before applying any threshold or phase-out calculation.

Why MAGI Exists

AGI measures income after above-the-line deductions — deductions Congress allows to reduce income before calculating tax. For certain targeted provisions, Congress wanted to ensure that taxpayers could not use specific tax preferences to artificially lower their income and thereby gain access to additional benefits. MAGI adds those preferences back, so that eligibility for the provision reflects a more complete picture of economic income.

The result: a taxpayer who reduces AGI through IRA contributions, foreign earned income exclusion, or student loan interest may still find themselves above the MAGI threshold for Roth IRA eligibility, Premium Tax Credits, or Medicare surcharges — because those items are added back in the relevant MAGI calculation.

Common MAGI Definitions and Their Add-Backs

Each provision specifies exactly what gets added back to AGI. The most frequently encountered MAGI definitions in practice are:

The most important practical implication: a taxpayer may be below the AGI threshold for a provision but still disqualified once the correct MAGI add-backs are applied. This is common for high-income earners who use Foreign Earned Income Exclusion, taxpayers with large IRA deductions, or those receiving excluded employer adoption assistance.

Key Provisions and MAGI Thresholds (2026)

Roth IRA Contribution Eligibility

Under IRC §408A, the ability to contribute directly to a Roth IRA phases out based on MAGI:

• Single / Head of Household: Phase-out $150,000–$165,000
• Married Filing Jointly: Phase-out $236,000–$246,000
• Married Filing Separately (if living with spouse at any point in the year): Phase-out $0–$10,000

Above the top threshold, direct Roth IRA contributions are completely disallowed. Taxpayers above these thresholds may use the backdoor Roth strategy — a non-deductible traditional IRA contribution followed by a Roth conversion — since Roth conversions have no income limit. See Mega Backdoor Roth and Solo 401(k) for advanced strategies.

Traditional IRA Deductibility

For taxpayers covered by a workplace retirement plan, the IRA deduction phases out at the following MAGI levels (2026):

• Single: Phase-out $79,000–$89,000
• Married Filing Jointly (covered spouse): Phase-out $126,000–$146,000
• Married Filing Jointly (non-covered spouse, covered spouse): Phase-out $236,000–$246,000

Taxpayers not covered by a workplace plan (and whose spouse is not either) may deduct the full IRA contribution regardless of income.

Premium Tax Credit (ACA)

The PTC uses MAGI in relation to the Federal Poverty Level (FPL). Households with MAGI between 100% and 400% of FPL are generally eligible, though the Inflation Reduction Act extensions through 2025 expanded eligibility above 400% FPL. The PTC calculation uses the applicable MAGI that adds back excluded foreign earned income — a provision relevant for U.S. citizens living abroad who otherwise have low U.S. AGI.

Medicare IRMAA

Medicare Part B and Part D premiums are subject to Income-Related Monthly Adjustment Amount (IRMAA) surcharges for beneficiaries whose MAGI exceeds base thresholds. IRMAA uses the beneficiary's MAGI from two years prior — so 2026 IRMAA is calculated on 2024 MAGI. For 2026, the base IRMAA threshold is $106,000 (single) / $212,000 (MFJ). MAGI for IRMAA purposes adds back tax-exempt interest to AGI, which can pull municipal bond investors into higher IRMAA brackets even if their taxable income appears modest.

MAGI vs AGI: A Practical Illustration

Consider a self-employed taxpayer who earns $200,000 and contributes $23,500 to a solo 401(k) and $7,000 to a traditional IRA. Their AGI is roughly $169,500 after SE tax deduction and retirement contributions. For Roth IRA MAGI purposes, the $7,000 IRA deduction is added back, giving MAGI of approximately $176,500 — below the $150,000 phase-out start (single), but above it for MFJ at $236,000. Whether the taxpayer can contribute to a Roth IRA depends entirely on which MAGI figure applies and which filing status governs.

The difference between AGI and MAGI is rarely a problem for most middle-income taxpayers. It becomes critical for:

• High-income earners approaching Roth IRA phase-outs, IRMAA brackets, or the NIIT threshold
• Expatriates and U.S. citizens abroad using the Foreign Earned Income Exclusion, who may have low AGI but high MAGI for ACA and IRA purposes
• Real estate investors evaluating the $25,000 passive activity loss allowance phase-out ($100,000–$150,000 MAGI)
• Business owners evaluating SALT cap phase-out planning after OBBBA

Tax Planning Around MAGI Thresholds

Because MAGI thresholds are bright-line cutoffs (especially for Roth IRA eligibility and IRMAA), marginal planning can produce outsized results:

• Harvesting capital losses: Reduces AGI from capital gains, which feeds into MAGI. Useful for taxpayers near IRMAA or NIIT thresholds.
• Timing business income: Cash-basis business owners can shift year-end invoicing or accelerate deductible expenses to manage the MAGI calculation in a specific year.
• Retirement plan contributions: Maximizing pre-tax contributions (401(k), SEP IRA, SIMPLE IRA) reduces AGI, which reduces most MAGI calculations — except where the plan contribution itself is added back (traditional IRA deduction in the Roth MAGI calculation).
• HSA contributions: Above-the-line, not added back for any standard MAGI calculation, making them a clean MAGI-reduction tool.
• Qualified Opportunity Zone investments: Deferring capital gain recognition reduces AGI and most MAGI calculations in the year of investment.

For the interaction between MAGI and the SALT cap phase-out under OBBBA, see SALT Cap $40,000 Planning Guide.

Related Terms

• Adjusted Gross Income — MAGI starts with AGI; understanding the above-the-line deductions that constitute AGI is prerequisite to any MAGI calculation
• Roth IRA — Roth IRA contribution eligibility is one of the most commonly encountered MAGI applications; phase-outs apply at $150,000–$165,000 single and $236,000–$246,000 MFJ (2026)
• Capital Gains — realized capital gains increase AGI and MAGI, potentially triggering NIIT (above $200,000/$250,000), IRMAA surcharges (Medicare), and Roth IRA phase-outs
• IRMAA (Income-Related Monthly Adjustment Amount) — Medicare premium surcharges calculated directly from MAGI two years prior; includes tax-exempt interest add-back; multiple Part B and Part D surcharge tiers

How CPAs Use MAGI in Practice

MAGI planning is most valuable at year-end and during mid-year projections, when there is still time to take action. CPAs typically build MAGI estimates for each relevant provision separately — not a single number — because the add-backs differ. For high-income clients, a MAGI projection matrix covering Roth eligibility, IRMAA, NIIT, and SALT phase-out gives a complete picture of threshold exposure and available planning levers. The goal is to identify which thresholds are closest, which produce the greatest marginal benefit from a dollar reduction, and which planning tools (HSA, retirement contributions, loss harvesting) are still available before year-end.