The MAGI Line on Form 1040: From Your W-2 to MAGI, Step by Step

By Kevin Luu, Co-Founder and Chief Learning Officer. Reviewed on 2026-09-30.

Form 1040 has no line labeled MAGI. Modified adjusted gross income starts from adjusted gross income, which is line 11a on the 2025 Form 1040 (line 11 on 2024 and earlier returns), and each tax rule then adds back a few items of its own. For a W-2 family with no foreign income, MAGI is usually the same number as line 11a.

The more useful question for a two-earner household with RSUs is how a $1 million-plus paycheck turns into that line 11a figure. Much of the work is done before the return is ever filed, on your W-2s, by choices you made in open enrollment. This guide walks the path from W-2 to MAGI line by line, with a worked example for a Seattle family and the California version of the same family.

Step 1: Your W-2 does not show MAGI, but Box 1 is where it starts

People often search for “MAGI on W-2”. There is no such box. What the W-2 gives you is Box 1, taxable wages, and that number flows straight to line 1a of Form 1040. Box 1 is already lower than your gross pay because the IRS tells employers to leave elective 401(k) and 403(b) deferrals out of it (IRS Instructions for Forms W-2 and W-3).

What is in Box 1 and what is not, for a typical tech or biotech employee:

One thing to notice: Box 5 (Medicare wages) is a different number. Pre-tax 401(k) and deferred comp deferrals are still in Box 5. That matters for the 0.9% Additional Medicare Tax, which is based on wages, not MAGI.

Step 2: From line 1a to line 11a on the 2025 Form 1040

Page 1 of the 2025 Form 1040 adds up income in a fixed order:

• Line 1a: wages from Box 1 of every W-2, including both spouses.
• Line 2a: tax-exempt municipal bond interest. It is reported for information only and is not added into total income.
• Lines 2b, 3b and 7a: taxable interest, ordinary dividends and capital gains, including gains when you sell RSU shares you kept after vest.
• Line 9: total income.
• Line 10: adjustments from Schedule 1, line 26, such as an HSA contribution you made outside payroll or a deductible IRA contribution.
• Line 11a: adjusted gross income. It is repeated as line 11b at the top of page 2.

The standard or itemized deduction comes after line 11a, so it never lowers MAGI. We explain that in does the standard deduction reduce MAGI.

Step 3: Apply the MAGI recipe for each rule

Each provision defines its own MAGI. For a W-2 family the add-backs are small or zero, so the work is mostly comparing line 11a with the 2026 thresholds for married couples filing jointly:

For more on each recipe, including what gets added back for the Roth IRA test, see which line is MAGI on Form 1040.

Worked example: a Seattle family at $1.19 million of pay

Assumptions (illustrative, 2026, married filing jointly, two children ages 4 and 8, Washington residents):

• Spouse A works at a large Seattle tech company: $200,000 salary plus $650,000 of RSUs vesting during the year. Defers $24,500 pre-tax to the 401(k) and puts the $8,750 family HSA maximum in through payroll.
• Spouse B is a director at a biotech company: $260,000 salary plus an $80,000 bonus. Contributes $24,500 to the Roth 401(k), defers $60,000 of pay into the company’s nonqualified deferred compensation plan (vested), and uses the $7,500 dependent care FSA (assuming the employer’s plan adopted the higher 2026 limit).
• Taxable account: $10,000 of interest, $15,000 of dividends, a $45,000 long-term gain from selling RSU shares held more than a year after vest, and $5,000 of municipal bond interest.

What $1,159,250 of MAGI means for 2026:

• Roth IRA: far above $252,000, so no direct contribution. A backdoor Roth is the route families at this income use.
• Child Tax Credit: zero. With two children ($4,400 of credit), the phase-out reaches zero at $488,000.
• NIIT: 3.8% of the lesser of investment income ($70,000) or MAGI over $250,000 ($909,250), so $2,660. Muni interest is not counted.
• SALT cap: 30% of MAGI over $505,000 is $196,275, which wipes out the increase, so the cap is the $10,000 floor.
• Additional Medicare Tax: measured on Box 5 wages, not MAGI. Their combined Medicare wages are $1,173,750 (gross pay minus the HSA and dependent care FSA, which are also outside Medicare wages), so 0.9% applies to $923,750 over the $250,000 joint threshold, about $8,314. Each employer withholds it only on wages above $200,000 from that employer, so expect a small balance on Form 8959.

What the pre-tax choices did, and what they did not do

The 401(k), HSA, deferred comp and dependent care elections kept $100,750 off line 1a. Without them, AGI would be $1,260,000. The Roth 401(k) did nothing to MAGI, by design: you pay tax now, and qualified withdrawals later are tax-free.

At this income, though, lowering MAGI by $100,750 crossed none of the lines in the table. Every one of those tests was already behind the family at $1,260,000 and still is at $1,159,250. The benefit is simpler: their taxable income is well above the $768,700 start of the 37% federal bracket for 2026 (Rev. Proc. 2025-32), so the $100,750 avoids or defers about $37,278 of federal income tax this year. The 401(k) and deferred comp amounts are taxed later, when paid out.

So for most families in our range, “how do I lower my MAGI” is the wrong question. The better questions are which year the deferred comp should be paid in, whether to sell concentrated RSU shares this year or next, and whether a larger vest pushes you past a threshold that uses a different measure. Two to watch for 2026: the AMT exemption phase-out starts at $1,000,000 of AMT income for joint filers (Rev. Proc. 2025-32), and California’s 1% Behavioral Health Services Tax applies to taxable income over $1,000,000 (2025 FTB rate schedules). More options are in how to reduce modified adjusted gross income.

Washington and California: the same paycheck, different state math

Washington. There is no tax on wages for 2026 (WA DOR), so the family’s state bill on pay is close to zero apart from payroll premiums such as the 0.58% WA Cares premium on wages. The 7% capital gains tax applies only to long-term gains above the standard deduction, which was $278,000 for 2025 (2026 not yet published) (WA DOR), so their $45,000 gain is likely below it. The bigger change is ahead. Washington enacted a 9.9% income tax on individuals and joint filers with AGI over $1,000,000, effective January 1, 2028. At today’s pay, this family’s AGI would be above that line. The detailed definition of income is still waiting on DOR guidance, but from 2028 a Washington family’s AGI may matter in a way it never has before, and the timing of deferred comp payouts and RSU sales is worth a fresh look then.

California. Move the same family to Palo Alto and their wages become taxable by California, and the income measure itself shifts. First, California does not recognize HSAs, so the $8,750 payroll HSA contribution is added back to California income on Schedule CA (FTB Schedule CA instructions). Second, the $45,000 RSU gain gets no lower rate, because California taxes all capital gains as ordinary income (FTB). Third, California in general does not conform to the One Big Beautiful Bill Act (FTB 2025 Form 540 booklet), which raised the federal dependent care FSA limit from $5,000 to $7,500 for 2026. FTB guidance for 2026 was not yet available when this was reviewed, so check whether the extra $2,500 must be added back for California. With California taxable income likely between $1,000,000 and $1,485,906, their marginal rate would be 12.3% on the 2025 joint schedule (11.3% plus the 1% tax over $1,000,000), and 1.3% California SDI is withheld on all wages with no cap for 2026 (EDD), including RSU vests.

Common mistakes when reading MAGI off a return

• Using gross pay or the offer letter number. Box 1 is already lower than gross pay. Start from line 11a, not from your total compensation.
• Using Box 1 for the Additional Medicare Tax. That tax uses Box 5, which still includes your 401(k) and deferred comp deferrals.
• Adding municipal bond interest back. It is not added for the Roth IRA, Child Tax Credit or NIIT tests.
• Assuming Roth 401(k) or mega backdoor contributions lower MAGI. Both are after-tax and stay in Box 1.
• Forgetting the RSU sale. The vest is in Box 1. Any gain after vest is a separate capital gain on line 7a and counts toward NIIT. See taxes on a brokerage account when you don’t sell.

What to write down for your kids

The open-enrollment elections and deferred comp choices in this example are decisions most parents make once and never explain. A one-page note in your FamilyKnowledge® Library, covering why you chose pre-tax or Roth, why you deferred pay into a plan with a given payout year, and what you expect to happen when it pays out, gives your children the reasoning behind the numbers, not only the account balances. As Kevin puts it: “Your kids will inherit your money. Will they inherit your judgment?”

Frequently asked questions

Is MAGI the same as line 11a?

For most W-2 families with no foreign income and no excluded savings bond interest, yes, for the Child Tax Credit, NIIT and SALT tests. The Roth IRA test subtracts Roth conversion income and adds back items like a deductible IRA contribution, so it can differ slightly. If your software filed Form 8960 or Schedule 8812, the MAGI it used is printed on that form.

Does a bigger RSU vest change my MAGI?

Yes, dollar for dollar. RSU shares are wages at vest, so their full value lands in Box 1 and line 1a. For a family already above $505,000, though, a larger vest usually crosses no new MAGI threshold. It raises ordinary income tax and, in California, state tax and SDI on the extra wages.

Does deferring pay into a nonqualified plan lower MAGI?

For the year you defer, a vested deferral under a 409A plan is generally left out of Box 1, so it lowers line 1a and MAGI. It is still subject to Medicare tax now, and it becomes taxable wages in the year it is paid out, which is why the payout schedule you choose matters as much as the deferral itself.

Next step

Pull last year’s return and both W-2s and compare gross pay, Box 1, Box 5 and line 11a side by side. If the gap between them is not something you can explain, or a deferred comp payout or large vest is coming, our tax management team can walk through it in a Tax & Wealth Assessment. Benefits elections are covered under retirement and employee benefits.

This is general education, and the right move depends on your family’s full picture.

Written by

Kevin Luu

Co-Founder and Chief Learning Officer, Bright Advisers

Kevin has advised high-income W-2 tech and biotech families since 2015, and leads the education-first Age Five Family Office from Brea, California.

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