GOP lawmaker: Health law rules will prevent smart hiring

"For many years, it has been customary for companies to provide their officers with non-taxable health insurance as part of their compensation and benefits package," Graves wrote. "Such plans sometimes require lower premiums from these employees than others."

The letter warned that many firms, particularly smaller ones, could be unfairly penalized under the Affordable Care Act depending on the rules' final phrasing.

The letter comes ahead of a Small Business hearing Wednesday on how firms are coping with the healthcare law's requirements.

It was addressed to Treasury Security Jack Lew and Steve Miller, acting commissioner of the Internal Revenue Service.