Under PPACA, health-care marketplaces were intended to provide a single point of access for individuals to enroll in private health plans, apply for income-based subsidies to offset the cost of these plans—which are paid directly to health-insurance issuers—and, as applicable, obtain an eligibility determination for other health coverage programs, such as Medicaid or the Children’s Health Insurance Program. CMS operates the federal Marketplace in about two-thirds of the states. To be eligible to enroll in a qualified health plan offered through a marketplace, an individual must be a U.S. citizen or national, or otherwise lawfully present in the United States; reside in the marketplace service area; and not be incarcerated (unless incarcerated while awaiting disposition of charges). Marketplaces, in turn, are required by law to verify application information to determine eligibility for enrollment and, if applicable, determine eligibility for the income-based subsidies. These verification steps include validating an applicant’s Social Security number, if one is provided; verifying citizenship, status as a national, or lawful presence by comparison with SSA or DHS records; and verifying household income and family size by comparison against tax-return data from IRS, as well as data on Social Security benefits from SSA. In particular, PPACA requires that consumer-submitted information be verified, and that determinations of eligibility be made, through either an electronic verification system or another method approved by HHS. To implement this verification process, CMS developed the data hub, which acts as a portal for exchanging information between the federal Marketplace, state-based marketplaces, and Medicaid agencies, among other entities, and CMS’s external partners, including other federal agencies. The Marketplace uses the data hub in an attempt to verify that applicant information necessary to support an eligibility determination is consistent with external data sources. For qualifying applicants, the act provides two forms of subsidies for consumers enrolling in individual health plans, both of which are paid directly to insurers on consumers’ behalf. One is a federal income tax credit, which enrollees may elect to receive in advance, which reduces a consumer’s monthly premium payment. This is known as the advance premium tax credit (APTC). The other, known as cost-sharing reduction (CSR), is a discount that lowers the amount consumers pay for out-of- pocket charges for deductibles, coinsurance, and copayments. Under PPACA, an applicant’s filing of a federal income tax return is a key element of “back-end” controls—those that occur later in the application or enrollment process, versus those occurring at the outset, or “front end.” When applicants apply for coverage, they report family size and the amount of projected income. Based, in part, on that information, the Marketplace will calculate the maximum allowable amount of APTC. An applicant can then decide if he or she wants all, some, or none of the estimated credit paid in advance, in the form of payment to the applicant’s insurer that reduces the applicant’s monthly premium payment. If an applicant chooses to have all or some of his or her credit paid in advance, the applicant is required to “reconcile” on his or her federal tax return the amount of advance payments the government sent to the applicant’s insurer on the applicant’s behalf with the tax credit for which the applicant qualifies based on actual reported income and family size. To facilitate this reconciliation process, the Marketplace sends enrollees Form 1095-A, which reports, among other things, the amount of APTC paid on behalf of the enrollee. This information is necessary for enrollees to complete their tax returns. The accuracy of information reported on this form, then, is important for determining an applicant’s tax liability, and ultimately, government revenues. As noted, PPACA requires that consumer-submitted information in applications for health-care coverage be verified, and CMS uses the data hub to check external data sources when making eligibility determinations. Hence, the extent to which federal agencies that support the verification system can provide or verify applicant information is a key element of the eligibility and enrollment process. Under the data hub process, verification efforts include the following: SSA: The agency responds to data hub inquiries with information from its records on applicant citizenship status, Social Security number, incarceration status, and death. In responding to data hub inquiries, SSA employs a two-step process: It first seeks to match an applicant’s name, Social Security number, and date of birth. If SSA can successfully establish this initial match, it will then seek to respond to other requests from the data hub for information, if made, based on specifics of a particular application, such as an applicant’s citizenship status. SSA also provides CMS with information on monthly and annual Social Security benefits paid to individuals under the Old Age, Survivors, and Disability Insurance program, if necessary to determine eligibility. IRS: The agency provides federal tax information on household income and family size, to be used for determining eligibility for insurance affordability programs, including the APTC and CSR subsidies. DHS: The agency provides applicant citizenship and immigration status information. If SSA cannot verify citizenship (as described above) and an applicant has also provided an immigration document number relating to citizenship, DHS will be asked to verify the applicant’s citizenship, or other immigration status. Or, if applicants have identified themselves as eligible noncitizens and provide immigration document information, DHS will be asked to verify that status. If the eligibility information applicants provide to the federal Marketplace cannot be verified through the external sources, such as SSA, IRS, and DHS, an inconsistency will result. In particular, an inconsistency can arise when the data hub query process yields no information; or when information is available through the data hub, but it does not match information the applicant has provided. CMS officials told us the key performance measures for the data hub are computer system availability and the extent to which transmissions of queries and responses are successfully accomplished; that is, that an inquiry is made and a corresponding reply received, without regard to content. According to CMS officials, the data hub only captures a code for type of reply that is generated when agencies respond to the inquiries, and those codes are not associated with any other applicant-identifying information or information that may have been provided in response to the query. There are no additional data kept on what information might have been transmitted in the source agency’s response, such as income or family size. Likewise, the data hub does not track whether information provided through the data hub matches information originally provided by the applicant, the officials said. Overall, although the data hub plays a key role in the eligibility and enrollment process, CMS officials said the agency does not track the extent to which the federal agencies deliver responsive information to a request, or, alternatively, whether they report that information was not available. From the standpoint of data hub operations, either outcome is valid, CMS officials told us, and the agency does not focus on the distinction. Additionally, CMS officials said they do not analyze data provided in response to data hub inquiries. By design, the data hub does not store individual transactional data that could be collectively analyzed over time. For policy reasons, the officials said, the agency did not want the data hub to become a data repository itself, and in particular, a repository of sensitive personal data. The CMS officials also said the agency is barred legally from maintaining IRS taxpayer information in the data hub. With CMS unable to provide us with information on data hub inquiry outcomes, we sought available information from the responding federal agencies. SSA, IRS, and DHS officials generally told us they do not analyze outcomes of data hub inquiries. Instead, they focus on responding to inquiries received. Our review also found that SSA, IRS, and DHS had limited information on the nature and extent of the inquiries made by the data hub. According to the three agencies, available statistics reflect data hub inquiries in general, and cannot be broken out by program, such as a qualified health plan or Medicaid. In addition, according to agency officials, an unknown number of data hub applicant inquiries were duplicates, which we could not eliminate from our examination. Instead, agency officials told us, they generally process inquiries sequentially as they are received from the data hub. Thus, while the agencies can provide some information on data hub queries, they cannot provide comprehensive information specifically on number of inquiries and individuals represented by those queries. Our examination of available statistics from SSA, IRS, and DHS, subject to the limitations noted, showed that while the agencies could successfully provide applicant verification information in a large percentage of cases, they nevertheless did not have data in their records to verify information for millions of data hub inquiries. SSA. According to statistics provided by SSA, the agency accomplished its match on name, Social Security number, and date of birth in a large majority of cases for PPACA’s first enrollment cycle, for 2014 coverage, as shown in table 1. However, for about 4.4 million inquiries—or about 5 percent of the total— the applicant information did not match SSA records. In addition, after completion of the name, Social Security number, and date of birth match, when SSA attempted to verify additional information, the agency could not confirm citizenship in about 8.2 million inquiries where individuals claimed they were citizens. We also obtained updated figures for the second enrollment cycle—for 2015 coverage. SSA’s total matching percentage was slightly higher (96.1 percent vs. 94.9 percent), and the number of unsuccessful citizenship queries was lower (3.6 million vs. 8.2 million), according to available data from SSA. IRS.