The Social Security Administration (SSA) oversees programs that touch the lives of millions of American families and are key components of the nation's economic safety net. The Old-Age, Survivors, and Disability Insurance (OASDI) program, commonly known as Social Security, is the most well-known of these programs. SSA is also responsible for carrying out two cash assistance programs for certain groups of low-income individuals: (1) Supplemental Security Income (SSI) for the Aged, Blind, and Disabled and (2) Special Benefits for Certain World War II Veterans. In addition to its core programs, the agency supports the administration of a number of non-SSA programs, such as Medicare, and provides and verifies data for a variety of federal and state program purposes. Benefit payments for SSA's core programs are considered mandatory spending , which means that such outlays are controlled by each program's authorizing statute—not by appropriations acts. However, the resources needed to carry out SSA's core programs, as well as to support the administration of other national priorities, are considered discretionary spending and thus are controlled by the annual appropriations process. This report provides background on SSA's core programs and related mandatory spending but its focus is on SSA's annual discretionary appropriations for administrative expenses. This report begins with a brief description of SSA's core programs and then examines its FY2017 projected spending on benefit payments and operating costs. Next, it discusses each component of the FY2017 President's budget request for SSA, including the agency's limitation on administrative expenses (LAE) account. Lastly, the report examines historical trends in the budget request and appropriation for SSA's LAE account. Most of the data presented in this report can be found in SSA's FY2017 budget justification to Congress, which is available at https://www.ssa.gov/budget/ . SSA's primary purpose is to administer several federal income support programs established under the Social Security Act, namely Social Security (OASDI; Title II of the act); Supplemental Security Income (SSI; Title XVI of the act); and Special Benefits for Certain World War II Veterans (Title VIII of the act). Social Security is a social insurance program that replaces a portion of an insured worker's income based on the individual's career-average earnings in covered employment. In contrast, SSI and Special Benefits for Certain World War II Veterans are public assistance programs that provide a guaranteed minimum income to certain groups of individuals who have little or no Social Security or other income. All three programs are entitlements , which means that the federal government is obligated to pay benefits to individuals who meet the eligibility requirements specified in each program's authorizing statute. To conform with data presented in SSA's FY2017 budget justification, this report describes the Old-Age and Survivors Insurance and Disability Insurance components of Social Security as separate programs. Old-Age and Survivors Insurance (OASI) provides monthly cash benefits to insured workers aged 62 or older and to their eligible spouses and children. It also pays benefits to certain survivors of deceased insured workers. Workers achieve insured status by working and paying Social Security taxes for a sufficient number of years in jobs that are covered under the Social Security system. OASI benefits and administrative costs are paid out of the Federal Old-Age and Survivors Insurance Trust Fund to which current workers, their employers, and self-employed individuals contribute. Under current law, the OASI trust fund's share of the combined 12.4% Social Security payroll tax rate is 10.03%. Social Security Disability Insurance (SSDI) pays monthly cash benefits to nonelderly insured workers who are unable to perform substantial work because of severe, long-term disabilities and to their eligible spouses and children. Workers become insured in the event of disability by working for a certain number of years in jobs that are covered under Social Security and thus are subject to payroll taxes. SSDI benefits are payable until the disabled worker dies, returns to work, or reaches Social Security's full retirement age (currently 66), at which point the worker transitions to OASI. SSDI benefits and administrative costs are paid out of the Federal Disability Insurance (DI) Trust Fund to which current workers, their employers, and self-employed individuals contribute. Under current law, the DI trust fund's share of the combined 12.4% Social Security payroll tax rate is 2.37%. SSI provides cash assistance to needy aged, blind, or disabled individuals, including blind or disabled children. The program's goal is to provide eligible individuals with a guaranteed minimum income to meet their basic needs for food, clothing, shelter, and other daily necessities. To qualify for SSI, a person must have limited income and assets and meet certain other requirements. Monthly SSI benefits are reduced by other countable income, meaning that SSI is often a program of "last resort" for low-income seniors and individuals with disabilities. States may complement the federal SSI benefit with state supplementary payments (SSP) that are made solely with state funds. Federal SSI benefits and administrative costs are paid out of general revenues. The Special Benefits for Certain World War II Veterans program provides a minimum cash benefit to two groups of low-income individuals living outside of the United States: American veterans of World War II and veterans of the Filipino armed forces that fought alongside the American military during that conflict. To qualify, individuals must have been aged 65 or older on December 14, 1999; have been SSI eligible for that month; be an eligible World War II veteran; have limited income; and reside outside the United States. The program's benefits and related administrative costs are paid out of general revenues. As shown in Figure 1 , in FY2017, spending on the OASI, SSDI, SSI, and Special Benefits for Certain World War II programs combined is projected to be more than $1.0 trillion. This projection includes benefit payments as well as SSA and non-SSA administrative expenses and certain other costs. Benefit payments account for approximately 98.4% of total projected spending. SSA estimates that the average number of federal beneficiaries of its core programs (adjusted for double counting) will be 68.4 million in FY2017. As noted earlier, benefit outlays for SSA's core programs are considered mandatory spending and therefore are not controlled by annual appropriations acts. Spending on benefit payments for these programs is determined by the eligibility requirements and payment levels specified in each program's authorizing statute. Table 1 shows administrative outlays for each core program as a percentage of benefit payments and for Social Security, as a share of trust fund income. The right column of the table excludes non-SSA administrative expenses and certain other costs, except in the row labeled "Total," which includes costs associated with Medicare. Administrative outlays as a share of benefit payments are greater for SSA's disability programs compared with the OASI program because the disability programs are more complex to administer and therefore require more resources per applicant or beneficiary. As a means-tested program, SSI is particularly complex to administer because SSA must verify all sources of income and resources available to an SSI applicant or recipient as well as the individual's living situation. The high ratio of administrative outlays to benefit payments under the Special Benefits for Certain World War II Veterans program is due primarily to low benefit levels and the steadily decreasing number of individuals in receipt of benefits. In FY2017, SSA projects that the program will pay benefits to fewer than 500 individuals on average. Although benefit payments for SSA's programs are considered mandatory spending and thus are not controlled by the annual appropriations process, the agency requires annual discretionary appropriations to carry out its programs and to support the administration of non-SSA programs, such as Medicare. SSA's accounts are traditionally funded via the Departments of Labor, Health and Human Services, and Education, and Related Agencies (LHHS) appropriations bill. This section of the report provides an overview of SSA's appropriations by examining the components of the FY2017 President's budget request for the agency. The report will be updated to reflect SSA appropriations passed by the House and the Senate Committees on Appropriations as well as the enacted appropriation for the fiscal year. For more information on the annual appropriations process, see CRS Report R42388, The Congressional Appropriations Process: An Introduction . The President's budget request to Congress for SSA currently consists of four accounts: (1) Payments to Social Security Trust Funds, (2) Supplemental Security Income Program, (3) Limitation on Administrative Expenses, and (4) Office of Inspector General. The limitation on administrative expenses (LAE) account funds the costs for carrying out SSA's core programs and for supporting the administration of non-SSA programs. The FY2017 President's budget request is summarized in Table 2 . The following section discusses each account in more detail. This account is designed to reimburse the OASI and DI trust funds for the costs of certain activities payable by general revenues. It consists of payments permanently and indefinitely authorized—and thus not controlled by annual appropriations acts—and payments controlled through the annual appropriations process. For FY2017, the President's budget projects $39.2 billion in payments that are not controlled by annual appropriations acts. Nearly this entire amount is from subjecting a portion of Social Security benefits to federal personal income tax. The remaining amounts are from reimbursement for union administrative expenses and payments related to changes in the reporting of self-employment income. For FY2017, the President's budget request includes $11.4 million in payments to the Social Security trust funds that are subject to the annual appropriations process.