Employers that realize they overpaid a health reform law-mandated “reinsurance” fee generally have until April 30 to seek a refund from the Centers for Medicare and Medicaid Services, regulators have disclosed.

In little-noticed guidance issued last week, CMS, a unit of the U.S. Department of Health and Human Services, said it “is aware” that some employers may have overpaid the Transitional Reinsurance Program fee.

Fee revenue is mostly used to partially reimburse insurers — under earlier government-set standards — covering those with high health care costs in the individual market.

Overpayments could occur for example, if an employer included health care plan participants, such as retirees enrolled in Medicare and receiving supplemental coverage from their former employers, who should have been excluded, as stipulated under 2013 HHS regulations, when calculating the amount they owed.

The 2014 fee is $63 per plan participant. Employers had until Dec. 5, 2014, to file an enrollment form with HHS that automatically calculated the amount of the fee. CMS says employers that now realize they gave an incorrect health plan enrollment count in filing the form should refile the form to receive a refund.

The deadline for employers to refile the form is April 30, or 90 days from when they originally filed the form, whichever is later. Unless an employer was late in filing the enrollment form, the deadline to refile in order to receive a refund would be April 30.

In addition, while the guidance is not clear, “it appears that in addition to refiling the form, plan sponsors must email a refund request to CMS at reinsurancecontributions@cms.hhs.gov”, benefit consultant Buck Consultants at Xerox reported in an alert released Wednesday.

In the two succeeding years of the three-year program, refund requests also must be filed within 90 days from the date an employer filed its enrollment form. The 2015 fee is $44 per plan participant, while the 2016 fee is $27 per plan participant.

The CMS announcement comes on the heels of a disclosure by HHS that it has collected $8.7 billion in 2014 reinsurance fee payments and anticipates collecting another $1 billion.

If that estimate is accurate, 2014 fee revenue would fall short of the $12 billion the Affordable Care Act stipulated was supposed to be collected. Of that $12 billion, $10 billion was to go to insurers in reinsurance payments and $2 billion to the U.S. Treasury Department.

That revenue shortfall “raises a concern that employers may be required to contribute yet additional amounts for 2014, or in higher future contribution rates,” said Rich Stover, a Buck Consultants principal in Secaucus, New Jersey.