WASHINGTON – Your medical plan is facing an unexpected expense, so you probably are, too. It’s a new, $63-per-head fee to cushion the cost of covering people with pre-existing conditions under President Barack Obama’s health care overhaul.

The charge, buried in a recent regulation, works out to tens of millions of dollars for the largest companies, employers say. Most of that is likely to be passed on to workers.

Employee benefits lawyer Chantel Sheaks calls it a “sleeper issue” with significant financial consequences, particularly for large employers.