Obamacare Sign-Up Deadline is Monday, March 31

NEW YORK (MainStreet) — Anyone who hasn't yet signed up for health insurance has only three days left to do so. Monday, March 31 is the open enrollment deadline for 2014 coverage. Starting April the exchanges will close to the general public, and only people with special circumstances will be able to apply for individual plans through the Affordable Care Act marketplaces such as healthcare.gov.

This deadline only applies to buying insurance through the ACA exchanges, so insurance companies will be free to sell plans directly to customers if they want to. It's uncertain how realistic that option will be, however, as the market for individual plans has largely migrated to the ACA exchanges. Americans who choose not to register before the deadline may not be able to get health insurance at all until next year.

March 31's deadline will also trigger the Affordable Care Act's mandate, so anyone who misses the deadline will be subject to penalties on next year's taxes. With all of this coming, here are a few details you might need to know.

Why is there a deadline in the first place?

The enrollment deadline is a necessary feature of the Affordable Care Act. One of the main goals of health care reform was to eliminate pre-existing conditions as a barrier to coverage. At the same time, though, private insurance as a concept only works if a company enrolls more healthy people than sick ones. Otherwise payments exceed premiums, the company bleeds money.

This is the much ballyhooed "death spiral."

If companies simply had to offer coverage at reasonable rates to everyone who walked through the door, as they now do, most of us would do the sensible thing: we would wait to buy insurance until en route to the hospital (typing with the hand that still moves). It would create a risk pool almost exclusively of the sick and injured.