As millions of people shop online for new insurance plans under President Barack Obama's healthcare reform law, about 10 per cent of applications to the main website are not being accurately transmitted, a government spokeswoman said on Friday.
The error rate has improved since HealthCare.gov's disastrous debut on October 1, which created a political crisis for Obama as opponents and supporters of the law questioned whether the most sweeping social programme since the 1960s was rushed well before it was ready.
Last week, the White House wrapped up a five-week emergency effort to fix the most obvious of the website's technical problems and between midnight on Sunday and noon on Friday, government health officials said 3.7 million people visited.
But the current level of mistakes deeper into the system are creating a new workload for insurers to verify the details of their new members and could lead to unwelcome surprises for consumers if there are mistakes in new policies that take effect on January 1.
HealthCare.gov relays information about new customers in so-called "834" transaction forms to the private insurance companies that provide the health plans. The portal serves people in 36 states while 14 states are running their own online marketplaces.
"We believe nine of 10 transactions are being successfully transmitted," the Centers for Medicare and Medicaid Services, or CMS, spokeswoman Julie Bataille said at a news briefing.
Previously, Bataille has said the majority of errors had been fixed in these transactions but had not defined either the current or past rate of mistakes.
She said the error rate has fallen, explaining that in the more than two months since October 1, HealthCare.gov could have experienced an error in as many as one in four transactions. Errors include forms not being generated, transmitting duplicate forms and of forms with technical data being passed incorrectly, she said.
Widespread errors in coverage could add to public complaints over the law's rollout and provide ammunition to Republican lawmakers who have campaigned all along to delay or replace the 2010 Affordable Care Act, commonly known as Obamacare.
"The new process put in place this week is making a difference. The enrollment files are getting better, but there is more work to do to ensure consumers are covered," Karen Ignani, the chief executive officer of insurance industry trade group, America's Health Insurance Plans (AHIP), said in a statement on Friday.