Start with Form SSA-1099

The Social Security Administration sends you a Form SSA-1099 each January showing how much SSDI you received in the previous year. This is your starting point. The form lists your total benefits in Box 5. You need this number before you can calculate what you owe.

If you did not receive a Form SSA-1099, contact Social Security at 1-800-772-1213 or visit your local office. You cannot estimate the amount — the IRS matches what Social Security reports, so your tax return must use the official figure.

Key Takeaways

  • You calculate tax on SSDI using the "combined income" formula, which includes half your benefits plus all other income, and only some SSDI is taxable even if your combined income is high.
  • Form SSA-1099 shows your total SSDI for the year; you will need this number and your other income (wages, interest, pensions) to do the calculation.
  • If your combined income is below the "base amount" for your filing status, you owe no federal tax on SSDI; base amounts are $25,000 for single filers and $32,000 for married filing jointly.
  • The IRS worksheet in the instructions to Form 1040 walks you through the calculation step by step, and tax software can do it automatically if you enter your SSA-1099 and other income.
  • You may owe tax even if you do not normally file a return, so check the thresholds before deciding whether to file.

Understand the Combined Income Threshold

The IRS does not tax all of your SSDI. Instead, it uses a two-tier system based on your combined income. Combined income is defined as your adjusted gross income (AGI) plus nontaxable interest plus half of your SSDI benefits. This is the number that determines how much, if any, of your SSDI is taxable.

Your filing status determines your base amount. If you file as single or head of household, your base amount is $25,000. If you file as married filing jointly, your base amount is $32,000. If you file as married filing separately, your base amount is $0 — meaning some of your SSDI will be taxable no matter what your income is.

If your combined income is at or below your base amount, none of your SSDI is taxable. You stop here and do not owe federal tax on your benefits. If your combined income exceeds your base amount, you move to the calculation.

Calculate Taxable SSDI Using the Two-Tier Formula

The IRS uses two tiers to determine how much SSDI becomes taxable. The calculation is mechanical but requires careful arithmetic.

Tier 1: Take the amount by which your combined income exceeds your base amount. Multiply that by 50 percent. This is your Tier 1 taxable amount, but it cannot exceed 50 percent of your total SSDI for the year.

Tier 2: If your combined income exceeds your base amount by more than $9,000 (single) or $12,000 (married filing jointly), you have a Tier 2 amount. Take the excess over that higher threshold, multiply it by 85 percent, and add it to your Tier 1 amount. The total cannot exceed 85 percent of your total SSDI.

The result is your taxable SSDI. You report this amount on your Form 1040 as income, and it is subject to federal income tax at your ordinary rate.

Work Through a Concrete Example

Suppose you are single, received $18,000 in SSDI in 2024, and had $12,000 in wages from part-time work. You have no other income and no nontaxable interest.

Your combined income is: $12,000 (wages) + $0 (nontaxable interest) + $9,000 (half of $18,000 SSDI) = $21,000. Your base amount is $25,000. Since $21,000 is below $25,000, none of your SSDI is taxable. You owe no federal tax on your benefits.

Now suppose you had $20,000 in wages instead. Your combined income is: $20,000 + $0 + $9,000 = $29,000. This exceeds your base amount of $25,000 by $4,000. Your Tier 1 taxable amount is $4,000 × 50% = $2,000. Since $2,000 is less than 50% of your total SSDI ($9,000), your taxable SSDI is $2,000. You report this on your tax return and pay tax on it at your ordinary rate.

Use the IRS Worksheet or Tax Software

The IRS publishes a worksheet in the instructions to Form 1040 that walks you through the calculation line by line. You can read the Form 1040 instructions from IRS.gov free of charge. The worksheet is labeled "Worksheet for Figuring Your Taxable Social Security Benefits" and appears in the section on Social Security benefits.

If you use tax preparation software — whether free software like IRS Free File, commercial software like TurboTax or H&R Block, or a tax professional — you enter your Form SSA-1099 and your other income, and the software calculates your taxable SSDI automatically. This is often faster and less error-prone than doing it by hand.

If you prepare your return by hand, work through the worksheet carefully. The calculation has multiple steps and is straightforward to make mistakes on. Double-check your arithmetic before you file.

Report Taxable SSDI on Your Return

On Form 1040, you report your total SSDI (from Box 5 of your SSA-1099) on line 5b. On line 5c, you report only the taxable portion that you calculated. The difference between these two numbers is your nontaxable SSDI.

If you file Form 1040-SR (the version for people 65 and older), the lines are the same. If you file a state income tax return, check your state's rules — some states do not tax SSDI at all, while others use the same federal calculation or a different one.

Decide Whether You Must File a Return

You must file a federal return if your gross income exceeds the threshold for your age and filing status. For 2024, if you are under 65 and single, your threshold is $14,600. If you are 65 or older and single, it is $18,350. These thresholds change each year.

Your gross income for this purpose includes your taxable SSDI plus all other income (wages, interest, pensions, self-employment income). Even if you have no income other than SSDI, if your combined income is high enough that some of your SSDI becomes taxable, you may have to file. Check the IRS thresholds for your age and filing status before deciding to skip filing.

Frequently Asked Questions

Do I have to pay tax on all of my SSDI?

No. The maximum amount of SSDI that can be taxed is 85 percent of your total benefits. If your combined income is below your base amount ($25,000 single, $32,000 married filing jointly), none of it is taxed. Most people with SSDI as their only income owe no federal tax on their benefits.

What if I have a spouse with income but we file separately?

If you file as married filing separately, your base amount is $0, meaning some of your SSDI will be taxable no matter what your income is. This filing status is almost always worse for SSDI recipients. Consult a tax professional about whether filing jointly or separately makes sense for your situation.

Does my state tax SSDI?

It depends on your state. Most states do not tax SSDI. Some states tax it using the same federal formula. A few states have their own rules. Check your state's tax agency website or ask a tax professional who knows your state's law.

What if I made a mistake on a return I already filed?

You can file an amended return using Form 1040-X. You have three years from the original filing date to claim a refund. If you owe more tax, there is no time limit, but the longer you wait, the more interest and penalties may accumulate. Consider consulting a tax professional if the error is large.

Can I get help calculating this if I am low-income?

Yes. The IRS runs the Volunteer Income Tax information (VITA) program, which offers free tax preparation at community centers, libraries, and senior centers. You can find a VITA site near you at IRS.gov. Many sites specialize in helping seniors and people with disabilities.