Per the GAO:
Our undercover testing for the 2016 coverage year found that the eligibility determination and enrollment processes of the federal and state marketplaces we reviewed remain vulnerable to fraud, as we previously reported for the 2014 and 2015 coverage years. For each of our 15 fictitious applications, the marketplaces approved coverage, including for 6 fictitious applicants who had previously obtained subsidized coverage but did not file the required federal income-tax returns. Although IRS provides information to marketplaces on whether health-care applicants have filed required returns, the federal Marketplace and our selected state marketplace allowed applicants to instead attest that they had filed returns, saying the IRS information was not sufficiently current. The marketplaces we reviewed also relaxed documentation standards or extended deadlines for filing required documentation. After initial approval, all but one of our fictitious enrollees maintained subsidized coverage, even though we sent fictitious documents, or no documents, to resolve application inconsistencies.
For each of our 15 fictitious applications, the federal or state-based marketplaces approved coverage at time of application—specifically, 14 applications for qualified health plans, and 1 application for Medicaid. Each of the 14 applications for qualified health plans was also approved for APTC subsidies. These subsidies totaled about $5,000 on a monthly basis, or about $60,000 annually. These 14 qualified-health-plan applications also each obtained CSR subsidies, putting the applicants in a position to further benefit if they used medical services.