Employers offering high-priced benefit plans to their workers may soon find themselves on a bumpy ride, thanks to the "Cadillac" tax.

According to the Medical Plan Trends Report, produced by benefit-management firm HighRoads and the member-advisory people at CEB, about 16 percent of plans are on track to incur the tax, charged on plans with annual premiums exceeding $10,200 for individuals or $27,500 for a family.

The 40 percent non-deductible tax takes effect in 2018 and is designed to discourage plans from including design features that promote over- or unnecessary use of medical care, such as low or non-existent deductibles and co-pays.