How AGI Affects Taxation of Retirement Distributions

Withdrawals from traditional IRAs, 401(k)s, and similar tax-deferred accounts are added to your taxable income for the year, which raises your adjusted gross income dollar for dollar. That higher AGI is what causes the real damage: it can push you into a steeper federal tax bracket, make more of your Social Security benefits taxable, trigger Medicare premium surcharges two years later, and shrink deductions and credits that are tied to income thresholds. Qualified Roth withdrawals sit outside all of this. Understanding how retirement distributions affect AGI is the difference between a predictable tax bill and an ugly surprise.

Which Withdrawals Count Toward AGI

AGI is your total income minus a short list of above-the-line deductions such as student loan interest, educator expenses, and deductible retirement contributions.¹ Almost every income-based threshold on your return starts from this number.

Withdrawals from a traditional IRA, SEP IRA, SIMPLE IRA, or traditional 401(k) are included in taxable income in the year you take them.² If your contributions were all pre-tax, the entire withdrawal is taxable. If you made nondeductible contributions along the way, only the earnings portion is taxed, and you report the split on Form 8606.

Qualified Roth IRA distributions are not included in gross income at all.³ The account must have been open for at least five tax years, and you must be at least 59½, disabled, or using up to $10,000 for a first-time home purchase. Because qualified Roth withdrawals never appear on your return, they have no effect on any of the downstream calculations below. That is what makes Roth balances so useful once you are drawing income.

Federal Tax Brackets

The federal system is progressive, so each additional dollar of taxable income is taxed at whatever bracket rate your total income reaches.⁴ A distribution stacks on top of pensions, interest, part-time earnings, and any taxable Social Security, so the dollars at the top of the pile are the ones that decide your marginal rate.

For 2026, the marginal brackets for single filers and married couples filing jointly are:⁵

10%: up to $12,400 (single) or $24,800 (joint)
12%: $12,401 to $50,400 (single) or $24,801 to $100,800 (joint)
22%: $50,401 to $105,700 (single) or $100,801 to $211,400 (joint)
24%: $105,701 to $201,775 (single) or $211,401 to $403,550 (joint)
32%: $201,776 to $256,225 (single) or $403,551 to $512,450 (joint)
35%: $256,226 to $640,600 (single) or $512,451 to $768,700 (joint)
37%: over $640,600 (single) or over $768,700 (joint)

The 2026 standard deduction is $16,100 for single filers and $32,200 for joint filers, and it comes off before the brackets apply.⁵ A single retiree with $30,000 in pension income and a $50,000 IRA withdrawal has $80,000 of gross income. After the standard deduction, taxable income is roughly $63,900, which places the top of the withdrawal in the 22% bracket. Without the distribution, the same retiree could have stayed entirely inside the 12% band.

Social Security Benefits Become Taxable

An IRA withdrawal can also make your Social Security benefits taxable through a formula called provisional income. Provisional income equals your AGI, plus any tax-exempt interest, plus half of your annual Social Security benefits.⁶ These thresholds are written into the statute and have never been adjusted for inflation, so they catch more retirees every year.

For single filers, provisional income between $25,000 and $34,000 can make up to 50% of benefits taxable. Above $34,000, up to 85% becomes taxable. For joint filers, the thresholds are $32,000 and $44,000.⁷

Here is where the math turns punishing. A $20,000 IRA distribution raises your AGI by $20,000, which raises your provisional income by $20,000, which can cause thousands of dollars of previously untaxed benefits to become taxable. You owe tax on the withdrawal itself and on the benefits it dragged onto your return. Retirees who plan only for the tax on the distribution amount often miss this second hit entirely.

Medicare Premium Surcharges (IRMAA)

Higher AGI also raises Medicare costs through Income-Related Monthly Adjustment Amounts. Medicare uses modified adjusted gross income from two years prior to set current premiums, so a large withdrawal in 2024 shows up in your 2026 premiums.⁸ The two-year delay is why the surcharge often arrives long after people have forgotten the withdrawal that caused it.

For 2026, the standard Part B premium is $202.90 per month. The IRMAA tiers for single filers are:⁹

$109,001 to $137,000: $81.20 Part B surcharge, plus $14.50 Part D
$137,001 to $171,000: $202.90 Part B, plus $37.50 Part D
$171,001 to $205,000: $324.60 Part B, plus $60.40 Part D
$205,001 to $499,999: $446.30 Part B, plus $83.30 Part D
$500,000 and above: $487.00 Part B, plus $91.00 Part D

Joint filers hit the same surcharge amounts but at tiers that begin at $218,001.⁹ At the top tier, a single retiree pays an extra $487.00 per month for Part B alone, adding $5,844 a year in premium surcharges. IRMAA is a cliff, not a slope: crossing a tier by a single dollar triggers the full surcharge for that tier, so precision matters when timing distributions.

One caution on appeals. Social Security will use a more recent tax year if you have had a qualifying life-changing event such as retirement, work stoppage, the death of a spouse, divorce, or loss of pension income. A one-time large IRA withdrawal is not a qualifying event. If you took a big distribution to pay off a mortgage and your income has since normalized, the surcharge stands.

Net Investment Income Tax

Retirement distributions are specifically excluded from the 3.8% Net Investment Income Tax.¹⁰ The withdrawal itself is never NIIT income. But because the NIIT applies once your MAGI passes $200,000 for single filers or $250,000 for joint filers (thresholds not indexed for inflation), an IRA distribution can push you over the line and expose your actual investment income to the tax.¹¹

Say you are single with $180,000 of AGI and $30,000 of dividend and capital gains income. You owe no NIIT, because your MAGI is below $200,000. Take a $40,000 IRA withdrawal and MAGI jumps to $220,000. You now owe 3.8% on the lesser of $30,000 (your investment income) or $20,000 (the excess over $200,000), which is $760 of NIIT you would not otherwise have owed.

Deductions and Credits That Shrink With Higher AGI

Medical Expense Deduction

You can only deduct medical expenses that exceed 7.5% of AGI.¹² Higher AGI lifts the floor. At $60,000 AGI, only expenses above $4,500 count. Add a $40,000 IRA distribution, AGI becomes $100,000, and the floor rises to $7,500. Retirees with chronic medical costs can watch this deduction disappear because of a single withdrawal.

Credit for the Elderly or Disabled

This credit is worth up to 15% of a $5,000 base for single filers, and it begins phasing out once AGI passes $7,500 for a single filer, with the credit cut by half of every dollar of AGI above the threshold.¹³ By $17,500 of AGI it is gone. For joint filers the phaseout starts at $10,000. If you rely on this credit, check the AGI math before taking more than you need from a traditional account.

When AGI Increases Stop Being Optional: RMDs

Starting at age 73, the IRS requires minimum withdrawals from traditional IRAs, 401(k)s, and similar accounts.¹⁴ Under the SECURE 2.0 Act, that age moves to 75 for people who turn 73 after December 31, 2032.¹⁵ Once RMDs begin, you no longer get to choose whether the withdrawal lands on your return. The required amount is computed from the account balance and a life expectancy factor, and it typically grows each year as the divisor shrinks.

Missing an RMD costs 25% of the shortfall, dropping to 10% if corrected within the correction window.¹⁶ Watch the first-year timing trap: if you delay your first RMD until April 1 of the year after you turn 73, you must take two RMDs in that second year. The doubled distribution can spike AGI enough to trigger higher Social Security taxation, jump an IRMAA tier, and shrink deductions all at once.

Roth IRAs have no RMDs during the original owner’s lifetime. Inherited Roth IRAs do carry distribution requirements, but qualified withdrawals stay off AGI. That gap is why gradual Roth conversions before RMDs begin are a common planning move.

Ways To Keep Distributions From Inflating AGI

Roth Conversions in Lower-Income Years

Converting a traditional IRA to a Roth adds the converted amount to gross income in the conversion year. Once inside the Roth, though, future qualified withdrawals are tax-free and invisible to AGI.³ The strategy tends to work best in the window between retirement and the start of Social Security and RMDs, when there is room in the lower brackets to absorb the conversion without setting off surcharges and phaseouts.

Qualified Charitable Distributions

If you are 70½ or older and give to charity anyway, a qualified charitable distribution sends up to $111,000 per person directly from your IRA to a qualified charity in 2026.¹⁷ The amount counts toward your RMD but is excluded from gross income, which keeps AGI down for Social Security taxation, IRMAA, and every AGI-linked deduction and credit. A married couple can each make a QCD from their own IRAs, for a combined $222,000 ceiling. The funds must go directly from the custodian to the charity. If the check lands in your hands first, the exclusion is lost.

Spreading Distributions Across Years

If you need a large sum, taking it in one year usually costs more than spreading it. Each year’s withdrawal has its own bracket space, so two $50,000 distributions in consecutive years typically produce a lower combined tax bill than one $100,000 distribution. The same holds for IRMAA: keeping each year’s MAGI below a tier avoids surcharges a single large withdrawal would trigger. Plan ahead, because IRMAA runs on a two-year lookback.

State Taxes Are a Separate Question

Everything above is federal. Most states with an income tax also tax traditional retirement distributions, but treatment varies widely. Some states exempt retirement income entirely, others offer partial exclusions that phase in at 59½ or 65, and some tax distributions at ordinary rates with no special break. Nine states have no income tax at all. If you are considering relocating in retirement, the state rules can materially change how much of each distribution you keep.

1
Internal Revenue Service. Definition of Adjusted Gross Income
2
Internal Revenue Service. Topic No. 451, Individual Retirement Arrangements (IRAs)
3
Office of the Law Revision Counsel. 26 USC 408A – Roth IRAs
4
Office of the Law Revision Counsel. 26 USC 1 – Tax Imposed
5
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026, Including Amendments From the One, Big, Beautiful Bill
6
Office of the Law Revision Counsel. 26 USC 86 – Social Security and Tier 1 Railroad Retirement Benefits
7
Internal Revenue Service. IRS Reminds Taxpayers Their Social Security Benefits May Be Taxable
8
Medicare.gov. 2026 Medicare Costs
9
Centers for Medicare & Medicaid Services. 2026 Medicare Parts A and B Premiums and Deductibles
10
Office of the Law Revision Counsel. 26 USC 1411 – Imposition of Tax
11
Internal Revenue Service. Topic No. 559, Net Investment Income Tax
12
Office of the Law Revision Counsel. 26 USC 213 – Medical, Dental, Etc., Expenses
13
Office of the Law Revision Counsel. 26 USC 22 – Credit for the Elderly and the Permanently and Totally Disabled
14
Internal Revenue Service. Retirement Topics – Required Minimum Distributions (RMDs)
15
Congress.gov. Required Minimum Distribution (RMD) Rules for Original Owners
16
Office of the Law Revision Counsel. 26 USC 4974 – Excise Tax on Certain Accumulations in Qualified Retirement Plans
17
Congress.gov. Qualified Charitable Distributions From Individual Retirement Arrangements