How to Calculate AGI With Social Security Income

To calculate your AGI when Social Security is part of the picture, you work in three steps: total your other gross income, run the combined income formula to find what portion of your benefits is taxable, add that portion to the rest, then subtract above-the-line adjustments. The result on line 11 of Form 1040 is your adjusted gross income. The tricky part is the middle step, because anywhere from zero to 85 percent of your benefits can land in the total.

Start With Your Other Gross Income

Federal law defines gross income broadly: wages, salaries, tips, taxable interest, dividends, capital gains, rental income, pensions, traditional IRA withdrawals, and most other money that comes in during the year.¹ Add all of that up first, leaving Social Security to the side. Benefits are the odd one out: they don’t automatically count as taxable income. A separate calculation decides how much of them joins the pile.

Find the Taxable Portion of Your Benefits

The IRS uses a figure called combined income to decide whether Social Security is taxable. Three numbers go into it:

All your other gross income for the year (wages, pensions, investment income, IRA withdrawals, and so on).
Tax-exempt interest, such as income from municipal bonds. You’ll find this on Form 1099-INT, box 8.²
Half of your total Social Security benefits, which is the net amount shown in Box 5 of your Form SSA-1099.³

Add those three and you have combined income.⁴ Note that tax-exempt interest, which is normally invisible on your return, gets pulled back in here. Retirees with a large municipal bond portfolio are sometimes surprised when that tax-free income helps push their benefits into the taxable range.

Now compare combined income to the statutory thresholds:⁵

Under $25,000 (single) or $32,000 (joint): none of your benefits are taxable.
$25,000–$34,000 (single) or $32,000–$44,000 (joint): up to 50 percent of your benefits are taxable.⁶
Above $34,000 (single) or $44,000 (joint): up to 85 percent of your benefits are taxable.

Those percentages are caps on how much of the benefit can be taxed, not tax rates. At least 15 percent of your benefits are always shielded from federal income tax.

The IRS Social Security Benefits Worksheet in the Form 1040 instructions walks through the exact arithmetic.⁷ You report total benefits on Form 1040, line 6a, and the taxable portion on line 6b.⁸

The Married Filing Separately Trap

If you’re married, lived with your spouse at any point during the year, and file a separate return, the base amount drops to zero. Up to 85 percent of your benefits become taxable regardless of how little you earned.⁵ The only escape is having lived apart from your spouse for the entire year, which restores the standard single-filer thresholds.

Thresholds That Don’t Move

The $25,000 and $32,000 base amounts are not indexed for inflation. Congress set them in 1983 and they have stayed there ever since.⁹ A modest income today easily crosses the line that was designed to catch higher earners four decades ago.

A Worked Example

Consider a single 67-year-old with:

Pension income: $20,000
Bank interest: $2,000
Tax-exempt municipal bond interest: $500
Social Security benefits from Box 5 of SSA-1099: $18,000
Traditional IRA deduction: $3,000

Combined income is $20,000 + $2,000 + $500 + $9,000 (half of $18,000) = $31,500. That exceeds the $25,000 base amount but stays below $34,000, so up to 50 percent of the benefits are taxable.

The excess over the base is $31,500 − $25,000 = $6,500. Half of that excess is $3,250. Compare that to half of total benefits ($9,000) and take the smaller: $3,250 is the taxable portion.

Now build gross income: $20,000 (pension) + $2,000 (interest) + $3,250 (taxable Social Security) = $25,250. Subtract the $3,000 IRA deduction, and AGI is $22,250. That’s the number that flows through the rest of the return.

Subtract Above-the-Line Adjustments

The final step is subtracting adjustments to income, which appear on Schedule 1 of Form 1040.¹⁰ Common ones include:

Deductible traditional IRA contributions.¹¹
Student loan interest, up to $2,500 per year if you meet income limits.
The deductible half of self-employment tax you paid.
Health insurance premiums for self-employed taxpayers not eligible for an employer plan.
HSA contributions.

Subtract the total from gross income and you have your AGI on line 11 of Form 1040. That figure controls eligibility for credits, deduction phase-outs, and other downstream calculations.¹²

Lump-Sum Back Payments

A lump-sum payment covering benefits owed from a prior year is normally taxable in full in the year you receive it, which can spike combined income and shove more of your benefits into the 85 percent tier. The IRS offers a lump-sum election method that lets you figure the taxable portion as if the back payments had been received in the earlier year they were meant to cover.⁷

You don’t file an amended return for the earlier year. Instead, you run the calculation both ways using worksheets in IRS Publication 915 and report whichever method produces the lower taxable amount on your current-year return. This comes up most often with disability back-pay awards, which can cover multiple years in a single check. Check the box on Form 1040, line 6c, if you elect this method.

Railroad Retirement Benefits

If you receive Tier 1 railroad retirement benefits, the Social Security Equivalent Benefit portion follows the same taxability rules. You’ll receive a Form RRB-1099 instead of an SSA-1099. Add the net amount from Box 5 of your RRB-1099 to any Social Security benefits on your SSA-1099 and use the combined total on the Benefits Worksheet.¹³ The same base amounts and 50/85 percent tiers apply.

Ways to Lower the Taxable Portion Next Year

Because combined income is the trigger, anything that lowers your other AGI can reduce how much Social Security becomes taxable.

Qualified Charitable Distributions

If you’re 70½ or older and own a traditional IRA, a qualified charitable distribution sends money directly from your IRA to an eligible charity. The distribution satisfies your required minimum distribution but never shows up in AGI. For 2026, you can direct up to $111,000 per year this way. A normal IRA withdrawal followed by a separate donation would increase AGI even if you later deduct the gift on Schedule A. The QCD skips that entirely, which can keep combined income under a threshold that would otherwise push benefits into the 85 percent tier.

Timing Roth Conversions

Converting a traditional IRA to a Roth adds the converted amount to gross income for the year. Doing conversions before you start collecting Social Security avoids inflating combined income during the years benefits are in play. Spreading conversions across several pre-claiming years keeps each year’s income bump smaller.

Drawing From Roth Accounts

Qualified Roth IRA distributions don’t count as gross income and don’t appear in the combined income formula. Leaning on a Roth for living expenses while minimizing traditional IRA withdrawals produces a lower combined income and can keep more of your Social Security tax-free.

Why the Number Matters Beyond April

Your AGI feeds into Medicare’s income-related monthly adjustment amount (IRMAA) surcharges on Part B and Part D premiums. Medicare looks at your tax return from two years prior, so your 2026 AGI will affect your 2028 premiums. For 2026, individuals with modified AGI at or below $109,000 (or $218,000 for joint filers) pay the standard premium with no surcharge; above those levels, surcharges rise through five tiers.¹⁴ If your income drops sharply between the reference year and now, you can request a new determination by filing Form SSA-44, which recognizes life-changing events including retirement, death of a spouse, divorce, and loss of a pension.¹⁵

One boundary worth naming: everything above is the federal calculation. A handful of states also tax Social Security benefits, using their own thresholds and exemptions that differ from the federal formula. If you live in one of those states, check your state’s department of revenue for the rules that apply to you.

1
Office of the Law Revision Counsel. Title 26 – INTERNAL REVENUE CODE, Part I – Definition of Gross Income, Adjusted Gross Income, Taxable Income, Etc.
2
Internal Revenue Service. Instructions for Schedule B (Form 1040) (2025)
3
Social Security Administration. Information for Tax Preparers
4
Internal Revenue Service. Social Security Income FAQs
5
Office of the Law Revision Counsel. 26 USC 86 – Social Security and Tier 1 Railroad Retirement Benefits
6
Internal Revenue Service. IRS Reminds Taxpayers Their Social Security Benefits May Be Taxable
7
Internal Revenue Service. Publication 915 (2025), Social Security and Equivalent Railroad Retirement Benefits
8
Internal Revenue Service. 1040 (2025) Instructions
9
Social Security Administration. Income Taxes on Social Security Benefits
10
Internal Revenue Service. 2025 Schedule 1 (Form 1040)
11
Internal Revenue Service. Credits and Deductions for Individuals
12
Office of the Law Revision Counsel. 26 USC 62 – Adjusted Gross Income Defined
13
RRB.Gov. Federal Income Tax and Railroad Retirement Benefits
14
Centers for Medicare & Medicaid Services. 2026 Medicare Parts A and B Premiums and Deductibles
15
Social Security Administration. Medicare Income-Related Monthly Adjustment Amount – Life-Changing Event