From Peter Suderman in Reason:

“The deadline to apply to enroll in health coverage and not pay a penalty next year is not the same deadline as the end of the open enrollment period, March 31. It’s actually February 15. Which means that while you can still enroll after February 15, you’ll have to pay the penalty for going uninsured if you finish your application after that date. What’s terrifying isn’t the earlier date itself, but the facepalm-worthy fact that the administration, including the Internal Revenue Service, seems not have known about the earlier date until very recently.”