Form 1040 prints AGI once. MAGI is that line after a second pass. The second pass changes with the rule you are testing. Roth IRA MAGI, NIIT MAGI, IRMAA MAGI, and ACA MAGI share a name. They are 4 calculations. People plan with W-2 wages or the AGI on a software summary, then lose Roth room or hit IRMAA or NIIT because they used the wrong one.
What is MAGI?
MAGI is adjusted gross income from Form 1040, line 11, plus or minus the items the rule you are testing tells you to put back. Each worksheet builds its own MAGI.
You start from the same AGI every time. Then you open the worksheet for Roth IRA contributions, the net investment income tax, Medicare IRMAA, or the premium tax credit. Those 4 worksheets each use their own add-back list.
What is MAGI vs AGI?
AGI is Form 1040, line 11 on every copy of your return. MAGI is rebuilt on the worksheet for the rule you are testing.
Software summaries often show AGI and stop. That covers bracket math after the standard or itemized deduction. A Roth contribution, an IRMAA letter, and Form 8960 ask for MAGI, and they mean their MAGI.
Why do Roth, NIIT, IRMAA, and ACA MAGI disagree?
They disagree because each statute names a different add-back list. Roth IRA MAGI subtracts taxable Roth conversions and adds back items such as the traditional IRA deduction. NIIT MAGI equals AGI for most filers, then adds back excluded foreign earned income. IRMAA MAGI is AGI plus tax-exempt interest. ACA MAGI is AGI plus tax-exempt interest, excluded foreign earned income, and the nontaxable part of Social Security.
Each statute publishes its own add-back list. Municipal bond interest that never hit AGI can move IRMAA MAGI and ACA MAGI and leave Roth MAGI and NIIT MAGI alone. A student loan interest deduction that lowered AGI comes back on the Roth worksheet among these 4.
What does Roth IRA MAGI add back?
IRS Publication 590-A Worksheet 2-1 starts with AGI, subtracts taxable Roth conversions and qualified-plan-to-Roth rollovers, then adds the traditional IRA deduction, the student loan interest deduction, the foreign earned income and housing exclusion, the foreign housing deduction, excluded savings-bond interest, and excluded employer adoption benefits.
For 2026, the IRS set the Roth IRA MAGI phaseout at $153,000 to $168,000 if you file single or head of household, and $242,000 to $252,000 if you file married filing jointly. Married filing separately, if you lived with your spouse during the year, phases out from $0 to $10,000. Those dollars come from the IRS 2026 retirement-limit notice and the 2026 update in Pub 590-A. The 2026 contribution limit is $7,500, or $8,600 if you are 50 or older.
A conversion that raised AGI comes off this MAGI. A year with a large conversion can look over the Roth phaseout on line 11 and under it on Worksheet 2-1. The conversion itself is a separate income event. See how a Roth conversion counts as income for the tax on the converted dollars.
What does NIIT MAGI add back?
Form 8960 instructions say MAGI equals AGI if you did not exclude income under section 911 and you do not own certain controlled foreign corporations or passive foreign investment companies. For most W-2 households, NIIT MAGI is the AGI on line 11.
If Form 2555 is on the return, you add back the foreign earned income exclusion, net of allocable deductions. CFC and PFIC holders make extra adjustments listed in those instructions. The 3.8% net investment income tax applies to the smaller of net investment income or MAGI minus the threshold. Form 8960 uses $200,000 if you file single or head of household, $250,000 if you file jointly, and $125,000 if you file separately. Those thresholds are written into the form instructions. Roth phaseouts change with the IRS inflation notice.
What does IRMAA MAGI add back?
SSA policy defines IRMAA MAGI as AGI from Form 1040, line 11, plus tax-exempt interest from line 2a. Municipal bond interest that never entered AGI is in this MAGI. The taxable part of Social Security stays inside AGI.
SSA uses a 2-year lookback. 2026 premiums generally use 2024 MAGI. For 2026, IRMAA starts at $218,000 MAGI if you file jointly and $109,000 for other statuses. Those thresholds are in the same SSA table. Convert this year, and the IRMAA MAGI that SSA reads is the later return.
What does ACA MAGI add back?
Form 8962 instructions build MAGI as AGI plus tax-exempt interest, Form 2555 amounts on lines 45 and 50, and the nontaxable portion of Social Security (line 6a minus line 6b). Household income then adds a dependent’s MAGI if that dependent must file.
Use the Form 8962 instructions for the year you are testing, including that year’s dollar cliffs and repayment caps.
Why do people plan with the wrong MAGI?
They copy W-2 box 1 or the AGI on a software summary and treat that figure as MAGI for every rule. Pretax 401(k) deferrals lowered box 1, so wages look smaller than total compensation. Municipal interest never hit AGI. A Roth conversion raised AGI. A student loan interest deduction lowered it. Those items do not move every MAGI the same way.
Take a joint return with AGI of $210,000 and $12,000 of tax-exempt municipal interest.
- Roth MAGI: $210,000. Worksheet 2-1 does not add municipal interest.
- NIIT MAGI: $210,000, if there is no Form 2555 and no CFC or PFIC adjustment.
- IRMAA MAGI: $222,000.
- ACA MAGI: $222,000, if Social Security is fully taxable and Form 2555 is blank.
The 2026 joint IRMAA threshold is $218,000. AGI of $210,000 looks under it. IRMAA MAGI of $222,000 is over it.
Take a single return with AGI of $148,000 after a $7,000 traditional IRA deduction and a $2,500 student loan interest deduction.
- Roth MAGI: $157,500.
- NIIT MAGI: $148,000.
- IRMAA MAGI: $148,000, if line 2a is $0.
- ACA MAGI: $148,000, on the same assumptions.
The 2026 single Roth phaseout starts at $153,000. AGI of $148,000 looks like a full $7,500 contribution. Roth MAGI of $157,500 is inside the phaseout. That is how Roth room closes on a number that never printed as MAGI.
Take a joint return with AGI of $248,000 that includes a $30,000 taxable Roth conversion.
- Roth MAGI: $218,000.
- NIIT MAGI: $248,000.
- IRMAA MAGI: $248,000, if line 2a is $0.
Roth MAGI is under the 2026 joint phaseout that starts at $242,000. NIIT MAGI is $2,000 under the $250,000 joint NIIT line. IRMAA MAGI is over the 2026 joint IRMAA line. Same AGI. Roth MAGI, NIIT MAGI, and IRMAA MAGI split. High-income W-2 years add RSU vests and bonuses on top of this. See tax strategies for high-income W-2 employees for the year-level projection those extras need.
Which MAGI worksheet should you open?
Name the rule first, then open that worksheet. Do not reuse a MAGI you computed for a different test.
- Direct Roth IRA contribution: Pub 590-A Worksheet 2-1.
- Net investment income tax: Form 8960, line 13.
- Medicare IRMAA: AGI plus Form 1040, line 2a.
- Premium tax credit: Form 8962 Worksheet 1-1.
Write the 4 numbers next to the 1 AGI. If a decision is close to a threshold, recompute the MAGI for that rule before you fund, convert, or sell.
How does Nino keep MAGI tests on one plan?
Nino models each MAGI from the worksheet that matches the rule, with a CFP and a CPA on the same household numbers for 1 flat annual fee. Roth room, NIIT, IRMAA, and Marketplace credits come from those 4 worksheets.
Book a demo if you want those MAGI tests on one plan. Through August 31, 2026, new members who start a one-year membership get $500 off their first year. Every plan includes a 30-day money-back guarantee.
