The NSA was designed to protect consumers from large, unexpected bills for out-of-network medical services, including life-flight transportation, certain emergency room bills, and procedures done outside the consumer's home network that the patient did not realize were outside the network.

Hoadley said all parties – providers, payors and service users – have made strides to facilitate the proper operation of the Act. While there was skepticism originally about whether providers and payors would make the system changes required, Hoadley says it appears that most have done so.

Employer- sponsored self-funded plan members are now enjoying the full protection of the Act, he said, since complaints from those members are now handled by federal adjudicators. Previously, self-funded plans had not enjoyed the same protections as fully funded plans, which could appeal "balance bills" to state agencies. States did not have the authority to hear self-funded plan member complaints about the charges.

"There's no difference now between fully funded and self-funded," he says. "Providers cannot balance bill the self-funded plans as they were able to do before the act was passed. "The act is good news for all employer plans. The law specifically addressed these issues to make sure they hit all types of insurance."

Among the study's findings:

• The Act appears to be protecting patients from the most pervasive forms of balance billing and getting consumers "out of the middle" of payment disputes between providers and payors.
• Physicians, hospitals, and payors have taken critical steps to adjust operational processes to mitigate the risk of consumers receiving balance bills for services covered by the NSA and to pay only in network cost sharing for those services.
• In general, state and federal regulators report relatively few NSA-related inquiries that rise to the level of violating the law.
• Cases related to self-funded plans are regularly transferred "in batches" electronically from HHS to the DOL, where benefit advisors provide further analysis and investigation.

Related: Survey: No Surprises Act prevented more than 2 million unexpected medical bills

The study's results notwithstanding, its authors noted that they were preliminary and could be somewhat misleading. Consumers could be paying balance bills without realizing it, due to the low level of health literacy in the U.S. Not all payors and providers have taken the administrative steps necessary to process balance bill claims. And there could be more claims in the pipeline that have not yet been processed, which would create a false sense of a low claims environment.

But overall the authors were satisfied that the NSA is working and saving consumers and plan sponsors money and time not spent fighting balance bills.

"One year after implementation of the NSA, informants largely agreed that consumers are being well-protected from surprise balance bills covered under the law," they wrote. "However, it is too early to assess whether the NSA will constrain the growth in health insurance premiums and encourage broader provider  networks, and concerns remain that coverage gaps in the NSA, such as for ground ambulance services,  can leave consumers with unexpected financial liability."