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Understanding Social Security Disability Insurance (SSDI) and Supplemental Security Income (SSI)

The Social Security Administration (SSA) manages two separate disability programs that serve different populations. SSDI, or Social Security Disability Insurance, is a program based on work history. If you or a family member has worked and paid Social Security taxes, you may have earned SSDI protection. This program provides monthly payments to workers who become unable to work due to a medical condition expected to last at least 12 months or result in death. Family members of disabled workers can also receive benefits based on that worker's earnings record.

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SSI, or Supplemental Security Income, operates differently. This program is needs-based, meaning it considers your income and resources rather than work history. SSI provides monthly payments to people age 65 or older, blind individuals, and disabled individuals who have limited income and resources. A person might have never worked or might not have sufficient work credits to receive SSDI, but could still receive SSI if they meet the financial limits.

The medical criteria for both programs are identical—the SSA uses the same definition of disability for determining who qualifies. However, the financial rules differ significantly. Under SSDI, there are work incentive provisions that allow you to earn money while still receiving benefits, at least temporarily. Under SSI, resource limits are much stricter, and unearned income affects your monthly payment amount.

According to the SSA, as of 2024, approximately 8.5 million people receive SSDI benefits, while about 7.5 million receive SSI. These programs represent a major source of income for millions of Americans with disabilities, yet many people are unfamiliar with the differences between them or unaware they might be eligible for one of these programs.

Practical Takeaway: Understanding whether you might fit into SSDI (work-history based) or SSI (needs-based) helps you understand which program's rules and limits apply to your situation. Both programs use the same medical criteria, but the financial rules are very different.

How the SSA Defines Disability

The Social Security Administration has a specific, legal definition of disability that applies to both SSDI and SSI. Under this definition, you must have a medical condition that prevents you from doing any kind of substantial work and is expected to last at least 12 months or result in death. This is a strict standard. The SSA does not grant benefits based on temporary conditions, minor impairments, or the inability to do just your previous job—you must be unable to work in general.

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The SSA maintains a list called the "Blue Book" that contains descriptions of medical conditions severe enough to meet the disability standard. These conditions span many categories: musculoskeletal disorders (like severe arthritis or back injuries), neurological conditions (like multiple sclerosis or epilepsy), cardiovascular diseases, respiratory conditions, mental health disorders, cancer, and many others. Having a condition on the Blue Book does not automatically mean you receive benefits, but it provides guidance about what level of severity the SSA typically considers disabling.

Beyond the Blue Book, the SSA evaluates disability using a five-step process. The SSA first considers whether you are working and earning substantial income. Then they determine whether your medical condition is severe enough to interfere with basic work activities. Next, they check whether your condition meets or equals a Blue Book listing. If not, they assess your remaining work capacity—what jobs might still be possible given your limitations. Finally, they consider whether jobs exist in the national economy that you could perform.

Medical evidence forms the foundation of any disability determination. The SSA reviews doctors' reports, hospital records, test results, and treatment history. They may request that you see a doctor they select for an evaluation. The strength and consistency of your medical evidence significantly affects the outcome of your case. Conditions that are well-documented with recent medical records have a better chance of resulting in a disability finding than conditions with minimal documentation or treatment.

Practical Takeaway: Disability, in the SSA's legal definition, means you cannot do any kind of substantial work, not just your previous job. Medical evidence is crucial, so keeping detailed records of your condition and treatment is important.

The SSDI Program: Work History and Family Benefits

SSDI operates as an insurance program. When you work and have Social Security taxes withheld from your paycheck, you are building an insurance policy. If you become disabled before retirement age, this work history provides protection for you. Additionally, your family members may receive benefits based on your earnings record if you are disabled, retired, or deceased.

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To be insured for SSDI, you generally need work credits. You earn work credits by working and paying Social Security taxes. In 2024, you earn one credit for each $1,730 of wages (this amount changes yearly). You can earn up to four credits per year. Most people need 40 work credits total, with at least 20 of those credits earned in the 10 years before becoming disabled. Younger workers may need fewer credits. The SSA calculates exactly how many credits you need based on your age when your disability begins.

A spouse of a disabled SSDI beneficiary can receive benefits at age 62 or any age if caring for the beneficiary's child under age 16. A former spouse can also receive benefits on the disabled worker's record under certain conditions. Children of a disabled worker can receive benefits until age 19 if in high school full-time, or until age 18 if not in school (age 19 if in high school). Adult children disabled before age 22 can receive benefits for life based on a parent's disability.

SSDI includes important work incentives. For example, you can earn a certain amount of money monthly without losing benefits—in 2024, this amount is $1,550 (called "substantial gainful activity" or SGA). Beyond this level, benefits stop, but the Impairment Related Work Expenses (IRWE) program allows you to subtract costs of work-related aids or assistance. The Plan to Achieve Self-Support (PASS) program lets you set aside income and resources to reach a work goal. These incentives exist to encourage work without immediately eliminating your safety net.

Practical Takeaway: SSDI is based on your work history and Social Security taxes you have paid. You can receive benefits and still earn some income through work incentive programs designed to help you return to work gradually.

The SSI Program: Income Limits and Resource Rules

SSI is a needs-based program, meaning the SSA looks at your current financial situation, not your work history. To receive SSI, your countable income must fall below a certain limit, and your countable resources must be under a resource limit. In 2024, the federal income limit for a single person is $943 monthly, and the resource limit is $2,000. For couples, the income limit is $1,415 monthly, and the resource limit is $3,000. Many states supplement these federal amounts with additional payments, so the actual limits in your state may be higher.

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"Countable income" means money SSA counts toward your limit. This includes wages from work, but also unearned income like interest, rental income, or payments from other people. However, SSA excludes certain income from the count. For instance, the first $65 per month of wages and half of remaining wages are not counted. This means you can work and earn some money while still receiving SSI. Additionally, many in-kind supports (like food or shelter provided by others) are partially excluded from income calculations.

"Countable resources" means assets the SSA counts toward your $2,000 limit. This includes bank accounts, stocks, bonds, and real estate (with some exceptions). However, your primary home and one vehicle do not count as resources. Household goods and personal items do not count. Many states have different resource rules under their supplementary programs, sometimes allowing higher limits.

The SSI program offers "Plan to Achieve Self-Support" (PASS) and "Impairment Related Work Expenses" (IRWE) similarly to SSDI. A PASS plan lets you set aside income and resources specifically to reach a work goal without that money counting against your limits. IRWE lets you deduct work-related disability costs before calculating your countable income. These provisions recognize that people receiving SSI may want to work and may have special expenses related to their disability that work requires.

Practical Takeaway: SSI is based on current income and resources, not work