Monday is the deadline to sign up for private health insurance in the new online markets created by President Barack Obama’s health care law. So far, about 4 out of every 5 people enrolling have qualified for tax credits to reduce the cost of their premiums.

Here’s what you need to know:

– The deadline is Mar. 31 at midnight EDT for the states where the federal government is running the sign-up website; states running their own exchanges set their own deadlines.

– You can sign up online by going to HealthCare.gov or your state insurance exchange. If you don’t know what your state marketplace is called, HealthCare.gov will direct you.

-You can call 1-800-318-2596 to sign up by phone or get help from an enrollment specialist.

-Check online for sign-up centers that may be open locally, offering in-person assistance.

-If you started an application by Monday but didn’t finish, perhaps because of errors, missing information or website glitches, you can take advantage of a grace period. The government says it will accept paper applications until April 7 and take as much time as necessary to handle unfinished cases on HealthCare.gov.

-Be prepared for the possibility of long wait times.