How to Calculate Taxes on Social Security Benefits

To calculate the taxes on your Social Security benefits, add half your annual benefits to your adjusted gross income and any tax-exempt interest, compare that “combined income” figure to the IRS thresholds for your filing status, and then apply a two-tier formula that makes up to 50 percent or up to 85 percent of your benefits taxable. That taxable portion is added to your other income and taxed at whatever bracket applies to you. The dollar cutoffs are lower than many retirees expect: $25,000 for single filers and $32,000 for married couples filing jointly.

The Three Numbers You Need

The calculation only works if you have all three inputs in hand.

Your total Social Security benefits come from Form SSA-1099, which the Social Security Administration mails each January by the 31st. Look at Box 5, which shows your net benefits for the previous year.¹ Supplemental Security Income is a separate program; SSI payments are not taxable and do not appear on the SSA-1099.²

Your adjusted gross income comes from line 11 of Form 1040. AGI includes wages, pensions, investment income, IRA distributions, and most other income sources, minus certain above-the-line deductions.³ Do not include Social Security benefits in AGI for this calculation; they enter separately in the next step.

Your tax-exempt interest, usually from municipal bonds, appears on Form 1099-INT. It is tax-free on its own, but the IRS specifically pulls it back in for the Social Security calculation. Skipping it is a common mistake.

The Combined Income Formula

The IRS does not test your AGI alone. It uses a figure called combined income, which some publications call provisional income or modified AGI:⁴

Combined income = AGI + tax-exempt interest + one-half of Social Security benefits

Only half your benefits go into the formula, not the full amount. If you received $24,000 in Social Security, you add $12,000 to your other income when checking the thresholds. The result decides which taxable tier you fall into, and it feeds directly into the tier calculations below.

Thresholds by Filing Status

Congress set these thresholds in 1983 and 1993, and the amounts have never been indexed to inflation. The same dollar figures apply today.

For single filers, heads of household, and qualifying surviving spouses:⁵

Below $25,000: none of your benefits are taxable.
$25,000 to $34,000: up to 50 percent of benefits may be taxable.
Above $34,000: up to 85 percent of benefits may be taxable.

For married couples filing jointly:⁵

Below $32,000: none of your benefits are taxable.
$32,000 to $44,000: up to 50 percent of benefits may be taxable.
Above $44,000: up to 85 percent of benefits may be taxable.

The 50 and 85 percent figures describe how much of your benefit gets pulled into taxable income, not a tax rate. If $10,000 of your benefit becomes taxable, that $10,000 is added to your other income and taxed at whatever marginal rate you already fall into.

The 50 Percent Tier: How the Math Works

When combined income lands between the first and second thresholds, the taxable portion of your benefits is the lesser of two amounts:⁶

50 percent of your total Social Security benefits, or
50 percent of the amount your combined income exceeds the first threshold.

The “lesser of” comparison protects retirees who only slightly cross the threshold. Take a single filer who received $22,000 in Social Security, $18,000 from a pension, and $2,000 in tax-exempt municipal bond interest. Combined income is $18,000 + $2,000 + $11,000 (half of $22,000) = $31,000. That falls between $25,000 and $34,000.

The excess over $25,000 is $6,000. Half of that excess is $3,000. Half of total benefits is $11,000. The lesser figure, $3,000, is the taxable portion. The formula kept the taxable amount well under 50 percent of the actual benefit because the income only slightly exceeded the threshold.

The 85 Percent Tier: A Two-Layer Calculation

Once combined income crosses the second threshold ($34,000 single, $44,000 joint), the calculation stacks two pieces together.⁵

Consider a single filer with $20,000 in Social Security, $30,000 in other income, and $500 in tax-exempt interest. Combined income is $30,000 + $500 + $10,000 = $40,500.

The first step covers the gap between the two thresholds. For a single filer, that gap is $9,000 ($34,000 minus $25,000). Half of $9,000 is $4,500. Compare that to half of total benefits ($10,000). The lesser figure, $4,500, is the 50 percent tier piece.

The second step handles income above $34,000. The excess is $40,500 minus $34,000, or $6,500. Multiply by 85 percent to get $5,525.

Add the two pieces: $4,500 + $5,525 = $10,025. Then apply the cap. Eighty-five percent of total benefits ($20,000) is $17,000. Since $10,025 is less than $17,000, the taxable amount is $10,025.⁶

The cap matters at higher incomes. No matter how far your combined income climbs, the IRS can never tax more than 85 percent of your total Social Security benefits. When the two-tier formula produces a bigger number, the 85 percent ceiling controls.

Married Filing Separately Changes the Math

If you are married, file a separate return, and lived with your spouse at any point during the year, your base amount drops to zero. Up to 85 percent of your benefits can be taxable from the first dollar of combined income. The 50 percent tier disappears entirely.⁶ The IRS worksheet for this situation goes straight to multiplying combined income by 85 percent.⁵

The one exception is if you lived apart from your spouse for the entire year. In that case, you use the $25,000 single-filer thresholds.⁷

Lump-Sum Payments for Prior Years

If you received a retroactive Social Security payment covering prior years, the full amount shows up on the SSA-1099 for the year you received it. By default, the IRS treats the entire lump sum as current-year income, which can push combined income well above the 85 percent threshold in a single year.⁵

A lump-sum election lets you recalculate the taxable portion as if you had received the benefits in the years they were owed. Run the tax formula separately for each earlier year using that year’s income, subtract any benefits you already reported for those years, and compare the total to the default method. If the election produces a smaller taxable amount, you can use it.

You do not file amended returns for the earlier years. The recalculated taxable figure still goes on your current-year return. Check the box on Form 1040 line 6c to indicate you are using the election, and keep the completed worksheets with your records rather than attaching them. Once chosen, this method can only be revoked with IRS consent.⁵

Reporting the Result on Form 1040

Once you have the taxable amount, reporting is quick. Enter total benefits from Box 5 of the SSA-1099 on line 6a. Enter the taxable portion on line 6b.⁸ If none of your benefits are taxable, enter zero on line 6b.

IRS Publication 915 contains Worksheet 1, which walks through every line of the calculation. Most tax preparation software runs it automatically. If you file by hand or want to double-check the software, that worksheet is the official reference.⁵

A Note on State Taxes

Everything above applies to federal tax only. Most states either exempt Social Security benefits entirely or do not levy a state income tax. As of 2026, eight states impose some form of state income tax on Social Security benefits, though most of those provide their own exemptions or deductions that shield lower-income retirees. Rules, income limits, and exemption amounts vary. If your state has an income tax, check whether it follows the federal approach, uses its own thresholds, or exempts benefits altogether before assuming the federal number carries over.

1
Social Security Administration. Get Tax Form (1099/1042S)
2
Internal Revenue Service. Regular and Disability Benefits
3
Internal Revenue Service. Adjusted Gross Income
4
Social Security Administration. Income Taxes on Social Security Benefits
5
Internal Revenue Service. Publication 915, Social Security and Equivalent Railroad Retirement Benefits
6
Office of the Law Revision Counsel. 26 USC 86 – Social Security and Tier 1 Railroad Retirement Benefits
7
Internal Revenue Service. Social Security Income
8
Internal Revenue Service. Publication 915, Social Security and Equivalent Railroad Retirement Benefits – Section: How To Report Your Benefits