Can I just sign up for Obamacare once I'm sick?

You can only sign up for insurance on the Obamacare exchanges through March 31.

NEW YORK (CNNMoney)

Myth: I'll just sign up for Obamacare when I get sick.

Reality: Actually, it doesn't work that way.

We've heard from many readers, particularly those in their 20s and 30s, who say they plan to forgo getting health insurance in 2014 and just pay the annual penalty of 1% of their income (or $95 if that number is lower) next year.

Coverage on the state-based exchanges can cost $200-$300 a month for many people. That's why some young adults without any major health issues think that it's only worth signing up for Obamacare if they get really sick or wind up in an accident.

But Americans can only sign up for coverage and subsidies on the exchanges during a specified enrollment period. For 2014, it runs through March 31.

If a person misses that deadline, they can still get health insurance next year, though they won't be eligible for an exchange policy or a subsidy. People can enroll in individual policies outside of the exchanges at any time.

Individuals that still want to sign up for Obamacare after March 31 have to wait until 2015 for coverage. (That enrollment period will run from Oct. 15 through Dec. 7 of next year.)

There are some exceptions though. If you experience a major life event, such as marriage, divorce, birth of a child or job loss, you can enroll for Obamacare at any time.

And those eligible for Medicaid or the Children's Health Insurance Program (CHIP) can also sign up at any time of the year.