Enrollment records for close to 15,000 HealthCare.gov shoppers were not initially transmitted to the insurance plans they selected, according to a preliminary federal estimate released Saturday. 
 
 While these cases pose a challenge for the Obama administration, officials say they believe the situation is improving. Since early December, fewer than 1 percent of HealthCare.gov enrollments did not make their way to health insurance plans. 
 
 "The vast majority of the work is retroactive," Centers for Medicare and Medicaid Services (CMS) spokeswoman Julie Bataille said in an interview Friday. "We're making sure that as we do the intense data reconciliation, we identify the things that need to be resolved so consumers can confirm they're enrolled." 
 
 The preliminary estimate that fewer than 15,000 enrollments failed to reach carriers comes from a recently completed federal analysis that compared the number of shoppers who clicked "enroll" with the number of digital files HealthCare.gov fired off to health-insurance plans. 
 
 That analysis does not generate a list of specific shoppers whose enrollment files were never sent, but rather provides a ballpark estimate of the discrepancy between enrollments finished and reports generated. The federal government does not have a list of people whose sign-up forms were never sent to their insurer. 
 
 Still, the figure is one of the more concrete measures of the data errors that have plagued the back-end of HealthCare.gov and challenged the Web site's ability to notify health-insurance providers when a new member enrolls in their products. 
 
 Those digital files are known in the insurance industry as "834 transmissions," and they have become the focus of much attention since insurers noticed some arriving with flaws or in duplicate. 
 
 Of particular concern to health insurers were situations in which a shopper thought he or she had signed up but the exchange did not notify the carrier. While insurance plans could plausibly correct inaccurate data, they could not get coverage to a subscriber they did not know existed. 
 
 During the first two weeks of October, the new federal analysis estimates, nearly 10 percent of enrollments were missing an 834 transmission. That number rose to 15 percent in mid-October before steadily declining through November. 
 
 From late November into early December, CMS estimates that less than 1 percent of sign-ups failed to send a record to the health insurer, indicating that a suite of software fixes have helped address the problem. 
 
 The missing enrollment files are one of three problems with the 834 transmissions that the federal government has identified. The other two are enrollment transmissions being sent in duplicate and those that are sent with inaccurate, or missing, data. 
 
 The federal government has repeatedly urged shoppers to reach out to their health insurance plan to confirm their enrollment and to pay their first month's premium, which is required before the insurer begins to pay doctors' bills. 
 
 Earlier this week, Health and Human Services sent the hundreds of insurers who sell on HealthCare.gov reams of data on who the federal government believed had enrolled in their products. That information, known as a "pre-audit file," is meant to allow insurers to reconcile their own lists of enrollees with the lists of those the federal government believes have signed up. 
 
 "All the files are available, so now people are at the beginning of that process of doing the matching," Andy Slavitt, vice president of Optum/QSSI, said at conference held Thursday by America's Health Insurance Plans. 
 
 While insurers are still analyzing the data, some say they are initially seeing fewer discrepancies than they had initially expected. Another file will be sent to insurers after Dec. 23, the last day for shoppers to sign up for coverage that begins Jan. 1. 

 Insurers and federal officials sifting through insurance applications under the health-care law have identified a raft of errors, including missing customers and inaccurate eligibility determinations that mean people may be enrolled in the wrong coverage. 
 
 Thousands of insurance applicants from HealthCare.gov—at least one in five at the height of the problems by one estimate—have received inaccurate assignments to Medicaid or to the marketplace for private plans, or have received incorrect denials, people familiar with the...
– The White House is releasing new data on the effectiveness of HealthCare.gov, and many of the figures aren't pretty. The Washington Post reports that the registrations of nearly 15,000 people who signed up for plans failed to arrive in insurers' inboxes, at least at first. Things have gotten better, however, since the start of this month, the administration says: Now, less than 1% of the registrations aren't getting to the firms. Still, officials don't actually have a list of names of those who suffered the problem. The so-called "orphan files" are just one of several issues highlighted in the Post and Wall Street Journal. In some cases, insurers got inaccurate data from the exchanges. Meanwhile, thousands of users were incorrectly assigned either to Medicaid or to private insurers, or their eligibility was wrongly denied; at their worst, these problems may affected up to a fifth of applicants, per an estimate cited by the Journal. Some legal immigrants in Illinois, for instance, were informed they'd get Medicaid coverage despite not having lived in the state long enough to qualify. An administration rep emphasizes that "the vast majority of the (newly-released data) is retroactive."