This article concerns proposals to change the Social Security system in the United States. Social Security is a social insurance program officially called "Old-age, Survivors, and Disability Insurance" (OASDI), in reference to its three components. It is primarily funded through a dedicated payroll tax. During 2015, total benefits of $897 billion were paid out versus $920 billion in income, a $23 billion annual surplus. Excluding interest of $93 billion, the program had a cash deficit of $70 billion. Social Security represents approximately 40% of the income of the elderly, with 53% of married couples and 74% of unmarried persons receiving 50% or more of their income from the program. An estimated 169 million people paid into the program and 60 million received benefits in 2015, roughly 2.82 workers per beneficiary. Reform proposals continue to circulate with some urgency, due to a long-term funding challenge faced by the program as the ratio of workers to beneficiaries falls, driven by the aging of the baby-boom generation, expected continuing low birth rate, and increasing life expectancy. Program payouts began exceeding cash program revenues (i.e., revenue excluding interest) in 2011; this shortfall is expected to continue indefinitely under current law.

Social Security has collected approximately $2.8 trillion more in payroll taxes and interest than have been paid out since tax collection began in 1937. This surplus is referred to as the Social Security Trust Fund. The fund contains non-marketable Treasury securities backed "by the full faith and credit of the U.S. government". The funds borrowed from the program are part of the total national debt of $18.9 trillion as of December 2015. Due to interest, the Trust Fund will continue increasing through the end of 2020, reaching a peak of approximately $2.9 trillion. Social Security has the legal authority to draw amounts from other government revenue sources besides the payroll tax, to fully fund the program, while the Trust Fund exists. However, payouts greater than payroll tax revenue and interest income over time will liquidate the Trust Fund by 2035, meaning that only the ongoing payroll tax collections thereafter will be available to fund the program.

There are certain key implications to understand under current law, if no reforms are implemented:

• Payroll taxes will only cover about 79% of the scheduled payout amounts from 2034 and beyond. Without changes to the law, Social Security would have no legal authority to draw other government funds to cover the shortfall.
• Between 2021 and 2035, redemption of the Trust Fund balance to pay retirees will draw approximately $3 trillion in government funds from sources other than payroll taxes. This is a funding challenge for the government overall, not just Social Security. However, as the Trust Fund is reduced, so is that component of the National Debt; in effect, the Trust Fund amount is replaced by public debt outside the program.
• The present value of unfunded obligations under Social Security was approximately $11.4 trillion over a 75-year forecast period (2016-2090). In other words, that amount would have to be set aside in 2016 so that the principal and interest would cover the shortfall for 75 years. The estimated annual shortfall averages 2.49% of the payroll tax base or 0.9% of gross domestic product (a measure of the size of the economy). Measured over the infinite horizon, these figures are 4.0% and 1.4%, respectively.
• The annual cost of Social Security benefits represented 4.0% of GDP in 2000 and 5.0% GDP in 2015. This is projected to increase gradually to 6.4% of GDP in 2035 and then decline to about 6.1% of GDP by 2055 and remain at about that level through 2086.

President Barack Obama opposed privatization (i.e., diverting payroll taxes or equivalent savings to private accounts) or raising the retirement age, but supported raising the annual maximum amount of compensation that is subject to the Social Security payroll tax ($137,700 in 20) to help fund the program. In addition, on February 18, 2010, President Obama issued an executive order mandating the creation of the bipartisan National Commission on Fiscal Responsibility and Reform, which made ten specific recommendations to ensure the sustainability of Social Security.

Federal Reserve Chairman Ben Bernanke said on October 4, 2006: "Reform of our unsustainable entitlement programs should be a priority." He added, "the imperative to undertake reform earlier rather than later is great." The tax increases or benefit cuts required to maintain the system as it exists under current law are significantly higher the longer such changes are delayed. For example, raising the payroll tax rate to 15% during 2016 (from the current 12.4%) or cutting benefits by 19% would address the program's budgetary concerns indefinitely; these amounts increase to 16% and 21% respectively if no changes are made until 2034. During 2015, the Congressional Budget Office reported on the financial effects of various reform options.