CMS had expected more than half of Medicare providers to be exempt from the new Merit-based Incentive Payment System (MIPS) in its first year. That ended up being a low estimate, as CMS said 65 percent have been notified they won’t be participating in MIPS for 2017.

A spokesperson for the agency told HealthExec that a total of 806,879 clinicians will be notified they won’t have to participate. Some 418,489 clinicians will have to participate in one of the “pick your pace” options this year to avoid a negative payment adjustment for 2019.

When asked why the estimate included in the final rule implementing the Medicare Access and CHIP Reauthorization Act (MACRA), the CMS spokesperson said the original projections was based on “best data CMS had to present at that time.” The actual eligibility determinations were based on a different time frame than the final rule, running from September 2015 to August 2016, with a “60-day claims run out rather than a flat calendar year.”

The spokesperson also cautioned that the participation number doesn’t include clinicians in the Advanced Alternative Payment Models track. Factoring those participants in, as well as clinicians participating in MIPS as a group, will mean a higher participation total.

Clinicians may be exempt for several reasons, most commonly because they fall under the low-volume threshold for MIPS. To be MIPS eligible, clinicians have to bill $30,000 or more in Medicare Part B allowed charges a year and provide care to more than 100 Part B-enrolled Medicare beneficiaries a year.

These exemptions are judged at the reporting-entity level, meaning some clinicians who would be exempt individually would have to participate if they’re reporting as a group.