The 111 th Congress enacted the Patient Protection and Affordable Care Act ( P.L. 111-148 , PPACA) and the Health Care and Education Reconciliation Act of 2010 ( P.L. 111-152 ). On January 19, 2011, the House passed H.R. 2 , which would repeal PPACA. Nonetheless, it is possible that the 112 th Congress will examine other legislation to amend parts of PPACA. During any debate to amend PPACA, one issue that may arise is the eligibility of aliens (noncitizens) for some of the key provisions of the act. This report discusses alien eligibility for the provisions in PPACA that have restrictions based on immigration status: participation in high-risk pools, the requirement to maintain health insurance, the ability to purchase insurance through an exchange, and eligibility for premium credits and cost-sharing subsidies. The report concludes with an analysis of data from the Current Population Survey (CPS) that illuminate some of the possible effects of PPACA on the health insurance coverage of the noncitizen population. Table 1 presents the definitions of some of the terms related to the noncitizen population and several of the different immigration statuses. In addition, because alien eligibility under PPACA is governed by the term "aliens who are lawfully present," the table outlines which aliens are considered to be lawfully present. Using the March 2010 Current Population Survey (CPS), the Congressional Research Service (CRS) estimated that as of March 2010 there were approximately 37.6 million foreign-born persons in the United States, approximately 12% of the U.S. population. The foreign-born population was comprised of approximately 16 million naturalized U.S. citizens and 21.6 million noncitizens. The literature often cites estimates published by the Pew Hispanic Center. Researchers at the Pew Hispanic Center used the same data but adjusted the survey weights to account for perceived noncitizen undercounts in the survey. They also assigned a specific immigration status (e.g., legal permanent resident, unauthorized alien) to each foreign-born survey respondent and used a methodology to estimate the illegally present population. The Pew Hispanic Center estimated that in March 2010 there were approximately 40.2 million foreign-born persons in the United States, and of the foreign-born population, approximately 14.9 million (37%) were naturalized U.S. citizens, 12.4 million (31%) were legal permanent residents (LPRs), 1.7 million (4%) were temporarily in the United States (i.e., nonimmigrants), and 11.2 million (28%) were estimated to be unauthorized (illegal) aliens. The following section discusses alien eligibility for the following provisions under PPACA: high-risk pools, the heath insurance mandate, the exchanges, and premium credits and cost-sharing subsidies. In general, aliens are separated into two groups for eligibility purposes under PPACA: aliens who are "lawfully present in the United States" are eligible for the provisions discussed below while aliens who are not "lawfully present in the United States" (i.e., unauthorized/illegal aliens) are ineligible. PPACA (§ 1101) required the Secretary of the Department of Health and Human Services (Secretary) to establish a temporary high-risk pool program to provide health insurance coverage for eligible individuals during the period beginning on the date the program was established and ending on January 1, 2014, the date when the exchanges will be operational. This program began offering coverage on August 1, 2010. Individuals are eligible for the high-risk pool if they have not been covered under creditable coverage during the six-month period prior to application for coverage in the high-risk pool and have a pre-existing condition as determined following guidance issued by the Secretary. To participate in the temporary high-risk pool program, a person must be a citizen or national of the United States or be lawfully present in the United States. Thus, unauthorized aliens are ineligible for participation in the high-risk pool program because they are not lawfully present in the United States. PPACA includes an individual mandate as of 2014 to maintain health insurance and has tax penalties for noncompliance. In other words, individuals—with some exceptions—who do not maintain acceptable health insurance coverage for themselves and their dependents would be required to pay a penalty. All aliens who are lawfully present are covered by the requirement to maintain health insurance. Unauthorized (illegal) aliens are expressly exempted from this mandate. In addition, the act specifies that a person is only considered lawfully present if the person is, and is reasonably expected to be for the entire period of enrollment, a U.S. citizen or national or an alien who is lawfully present in the United States. Until the exchanges are operational, it is unknown what the shortest period of enrollment will be and whether certain nonimmigrants who are in the United States for limited periods of time, in many cases under six months, would be covered by the mandate (e.g., tourists (B-visas), cultural exchange (J-visas), performers and athletes (O- and P-visas)). In addition, no penalty will be imposed on those without coverage for less than three months (with only one period of three months allowed in a year), so for aliens in the United States for less than three months (e.g., most tourists) there would be no consequences to not having health insurance. Because the penalties for noncompliance with the individual mandate are tax-based, the following section discusses the rules for taxation of noncitizens. In particular, understanding these rules might be important because there has been debate about the extent to which the Internal Revenue Service, in light of the limits PPACA places on enforcement, will be able to collect penalties from individuals who do not have other tax liability. To the extent that this might be a concern, it would seem to arise regardless of the individual's citizenship status. All foreign nationals working in the United States are subject to U.S. tax laws. For federal tax purposes, foreign nationals working in the United States are classified as resident or nonresident aliens. These terms are in the Internal Revenue Code (I.R.C.) but do not exist in the Immigration and Nationality Act (INA). As a result, the specific immigration statuses under the INA do not align directly with the terms resident and nonresident alien. In general, an individual is a nonresident alien unless he or she meets the qualifications under one of the following residency tests: Green card test: the individual is a lawful permanent resident of the United States at any time during the current year, or Substantial presence test: the individual is present in the United States for at least 31 days during the current year and at least 183 days during the current year and previous two years. For computing the 183 days, a formula is used that counts all the qualifying days in the current year, one-third of the qualifying days in the immediately preceding year, and one-sixth of the qualifying days in the second preceding year. While resident aliens are subject to the same tax treatment as U.S. citizens, nonresident aliens are subject to different treatment, such as generally being taxed only on income from U.S. sources. Nonetheless, their income that is "effectively connected" with a U.S. trade or business is generally taxed by the same rules and at the same rates as the income of U.S. citizens and resident aliens. There are several situations in which an individual may be classified as a nonresident alien even though he or she meets the substantial presence test. For example, an individual will generally be treated as a nonresident alien if he or she has a closer connection to a foreign country than to the United States, maintains a tax home in the foreign country, and is in the United States for fewer than 183 days during the year. Another example is that an individual in the United States under an F-, J-, M-, or Q-visa may be treated as a nonresident alien if he or she has substantially complied with visa requirements. Other individuals who may be treated as nonresident aliens even if they would otherwise meet the substantial presence test include employees of foreign governments and international organizations, regular commuters from Canada or Mexico, aliens who are unable to the leave the United States because of a medical condition, foreign vessel crew members, and athletes participating in charitable sporting events. Additionally, depending on where the individual is from, there may be an income tax treaty between that country and the United States with provisions for determining residency status. Under PPACA, "American Health Benefit Exchanges" will begin operation by 2014. An exchange cannot be an insurer, but it will provide eligible individuals and small businesses with access to insurers' plans in a comparable way. In addition, based on income certain individuals may qualify for a tax credit toward their premium costs and a subsidy for their cost-sharing; the credits and subsidies will be available only through an exchange beginning in 2014. The law allows all lawfully present noncitizens to purchase insurance through an exchange and bars unauthorized aliens from obtaining insurance through an exchange. Based on their income, certain individuals may qualify for a tax credit toward their premium costs and a subsidy for their cost-sharing; the credits and subsidies will be available only through an exchange beginning in 2014. All lawfully present aliens who meet specified criteria are eligible for the premium tax credit and cost-sharing subsidies. Unauthorized (illegal) aliens are ineligible for the tax credit and subsidies. In addition, the law provides specific rules for calculating the credits and subsidies for mixed-status families. Some have raised concerns that PPACA created an inequality between U.S. citizens and some noncitizens with incomes at or below 133% of the federal poverty level (FPL) with respect to eligibility to participate in an exchange and receive premium credits or cost-sharing subsidies.