Adjusted Gross Income is the single figure on Line 11 of your Form 1040; Modified Adjusted Gross Income is that same figure with specific deductions or excluded income added back so the IRS can see your fuller economic picture before granting a tax benefit. The comparison of modified adjusted gross income versus adjusted gross income comes down to one practical point: AGI is one number that drives your return, while MAGI is a family of numbers, each defined slightly differently depending on which credit, deduction, or premium calculation is at stake. For many W-2 earners the two figures are identical. For anyone with foreign income, tax-exempt interest, Social Security benefits, or a student loan interest deduction, they diverge.
How AGI Is Built
AGI starts with gross income and subtracts a specific list of deductions federal law allows before you reach the standard or itemized deduction.1Office of the Law Revision Counsel. 26 USC 62 – Adjusted Gross Income Defined Gross income covers wages, salaries, taxable interest, ordinary dividends, capital gains, business income, rental earnings, and retirement account distributions.
From that total, you subtract “above-the-line” deductions: contributions to a Health Savings Account, student loan interest paid, educator expenses, penalties for early withdrawal of savings, and the deductible portion of self-employment tax. Alimony paid under a divorce agreement executed on or before December 31, 2018 still qualifies; Congress repealed the deduction for agreements finalized after that date.1Office of the Law Revision Counsel. 26 USC 62 – Adjusted Gross Income Defined
The result lands on Line 11. It sets your tax bracket, drives many deduction phase-outs, and becomes the starting point for every MAGI calculation.
What MAGI Adds Back and Why
MAGI exists so the IRS can look past deductions and exclusions that would otherwise make a well-off taxpayer appear to earn much less. The most common add-backs are foreign earned income and foreign housing amounts excluded from gross income, and the student loan interest deduction. Depending on the provision, you may also add back your IRA deduction, tax-exempt bond interest, or the nontaxable portion of Social Security benefits.2Internal Revenue Service. Modified Adjusted Gross Income
If none of those items apply to you, MAGI equals AGI. That’s the outcome for many taxpayers with straightforward wages and no foreign earnings, particularly when they’re checking benefits like the Child Tax Credit or education credits, whose add-back lists are short.
Why MAGI Changes From One Benefit to the Next
The critical wrinkle most explanations miss is that there is no universal MAGI. Each tax provision has its own definition, and swapping them can cost real money.
For traditional IRA and Roth IRA purposes, MAGI is AGI figured after the rules for Social Security taxation and passive activity losses, but without counting the foreign earned income exclusion, the savings bond interest exclusion, the adoption assistance exclusion, the student loan interest deduction, or the IRA deduction itself.3Office of the Law Revision Counsel. 26 USC 219 – Retirement Savings4Office of the Law Revision Counsel. 26 USC 408A – Roth IRAs
For the passive activity rental loss allowance, the add-back list includes passive activity losses, nontaxable Social Security benefits, deductible IRA contributions, the self-employment tax deduction, and the student loan interest deduction, among others.5Internal Revenue Service. Instructions for Form 8582 (2025) The self-employment tax deduction gets added back for rental losses but not for IRA eligibility. Small differences like this are easy to overlook and expensive when missed.
For the Affordable Care Act premium tax credit, MAGI adds foreign earned income, tax-exempt interest, and nontaxable Social Security benefits back to AGI. For the Child Tax Credit and education credits, the add-backs are limited mainly to foreign earned income and foreign housing exclusions.2Internal Revenue Service. Modified Adjusted Gross Income A retiree with substantial Social Security income can have one MAGI for ACA purposes and a lower one for the Child Tax Credit in the same year.
Where the Difference Actually Matters
Traditional and Roth IRA Limits
MAGI decides whether you can deduct a traditional IRA contribution when you or your spouse is covered by a workplace retirement plan, and whether you can contribute to a Roth IRA at all. For 2026, a single filer covered by a workplace plan sees the traditional IRA deduction phase out between $81,000 and $91,000 of MAGI. A married couple filing jointly loses Roth IRA eligibility between $242,000 and $252,000. Married filing separately hits the phase-out almost immediately, between $0 and $10,000.6Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500 If neither spouse participates in an employer plan, the traditional IRA deduction is available regardless of income.
ACA Premium Tax Credits
For coverage year 2026, household MAGI must fall between 100% and 400% of the federal poverty level to qualify for premium tax credits through the Marketplace.7Internal Revenue Service. Eligibility for the Premium Tax Credit The temporary removal of the 400% cap that applied from 2021 through 2025 expired on January 1, 2026.8United States Congress. Enhanced Premium Tax Credit and 2026 Exchange Premiums For a single person in the 48 contiguous states, 400% FPL is $63,840; for a family of four, $132,000.9U.S. Department of Health and Human Services. 2026 Poverty Guidelines Exceeding the cap by a dollar wipes out the entire subsidy for the year. Because ACA MAGI includes nontaxable Social Security, retirees often miscalculate this one.
Medicare Premium Surcharges
Higher-income Medicare enrollees pay Income-Related Monthly Adjustment Amounts on top of standard Part B and Part D premiums. The lookback is two years: 2026 premiums are set from 2024 MAGI.10Social Security Administration. HI 01101.010 – Modified Adjusted Gross Income (MAGI) For 2026, an individual with MAGI at or below $109,000 (or a couple at or below $218,000) pays no surcharge; the top tier begins at $500,000 for individuals and $750,000 for joint filers, at $487.00 per month on Part B alone. Part D surcharges apply at the same brackets.11Centers for Medicare & Medicaid Services. 2026 Medicare Parts A & B Premiums and Deductibles A one-time income event, such as selling a business or converting a large traditional IRA to a Roth, can raise premiums two years later.
Net Investment Income Tax
The 3.8% Net Investment Income Tax applies to the lesser of net investment income or the amount by which MAGI exceeds $200,000 for single filers, $250,000 for joint filers, or $125,000 for married filing separately. Those thresholds are fixed in statute and have not been adjusted for inflation since the tax took effect in 2013.12Internal Revenue Service. Net Investment Income Tax
Family and Education Credits
The Child Tax Credit phases out above $200,000 MAGI for single filers and $400,000 for joint filers, dropping by $50 for every $1,000 over the threshold. The Adoption Tax Credit phases out for 2026 between $265,080 and $305,080.2Internal Revenue Service. Modified Adjusted Gross Income The American Opportunity and Lifetime Learning credits phase out between $80,000 and $90,000 for single filers, and between $160,000 and $180,000 for joint filers. The student loan interest deduction has its own phase-out, and because that deduction is itself an IRA-MAGI add-back, the calculation loops. IRS Publication 590-A and most tax software resolve it with iterative worksheets.13Internal Revenue Service. Publication 590-A (2025), Contributions to Individual Retirement Arrangements (IRAs)
How to Calculate Your Own MAGI
The steps are the same regardless of which benefit you’re testing, but the third step changes with the benefit.
- Pull your AGI from Line 11 of Form 1040.
- Identify the benefit you’re checking. IRA eligibility, ACA premium credit, IRMAA, NIIT, and each education or family credit have their own add-back lists.
- Look up the add-backs for that specific provision on the IRS MAGI page or in the instructions to the relevant form.2Internal Revenue Service. Modified Adjusted Gross Income
- Gather the supporting documents. Form 1098-E reports student loan interest paid. Form 2555 reports the foreign earned income exclusion.14Internal Revenue Service. Form 1098-E – Student Loan Interest Statement
- Add those items to your AGI and compare the result to the threshold that applies for the tax year in question.
If you have no foreign income, no tax-exempt interest, no nontaxable Social Security, and you’re not adding back a student loan interest or IRA deduction for the provision at hand, your MAGI equals your AGI and no further math is needed.
What Happens If You Get It Wrong
MAGI errors show up in two costly ways. First, contributing to a Roth IRA when your MAGI is over the limit triggers a 6% excise tax on the excess for each year it remains in the account. Withdrawing the excess and any earnings before your filing deadline, extensions included, avoids the penalty.15Internal Revenue Service. Retirement Topics – IRA Contribution Limits
Second, underestimating MAGI for advance ACA premium tax credits means paying the excess back at tax time. With the 400% FPL cap back in place for 2026, a household that estimated income below the cliff and actually landed above it can owe back the full year’s subsidy.
On the Medicare side, IRMAA isn’t a penalty, but the two-year lookback can produce a surprise increase that lasts a full year. If a life-changing event such as retirement, divorce, or the death of a spouse caused the income spike, you can ask the Social Security Administration for a redetermination by filing Form SSA-44.