What you need to know about Tuesday's open enrollment

1 What happens and why? Open enrollment begins for the online health insurance marketplaces, the centerpiece of the 2010 Affordable Care Act, open for business. People can begin shopping for insurance plans on the exchanges. Lower- and moderate-income people will be able to apply for tax subsidies to offset the cost of premiums or enroll in Medicaid in states expanding the program.

The initial open enrollment period for the marketplaces, which operate as interactive websites, runs from Oct. 1 through March 31. Most Americans are required to have insurance by Jan. 1, 2014, or face a fine, but officials have said those who are insured by April 1 won't be penalized. Insurance bought by mid-December will take effect Jan. 1; coverage bought by mid-March is effective April 1. For the first time, insurers will be barred from rejecting people with pre-existing conditions or charging them more.

2 What will you find on exchanges? Each state will have its own online marketplace, or exchange, and offer in-person help. The marketplaces will tell people if they are eligible for Medicaid, which many states are expanding, or if they should sign up for private plans.

There's help with co-payments and deductibles for people with incomes up to 250 percent of the poverty level ($28,725 for an individual or $58,875 for a family of four). If someone doesn't qualify but earns less than four times the federal poverty rate — $45,960 for an individual and $94,200 for a family of four — that person may qualify for subsidies to reduce the cost of the premiums. People who receive subsidies will be required to pay 2 to 9.5 percent of their incomes toward premiums, depending on how much money they make.

Individual policies will be organized into four tiers — bronze, silver, gold and platinum — depending on their coverage and costs.

3 Here are some key dates and facts to remember in the next phases of the health care law:

Jan. 1, 2014: Coverage obtained on the exchanges goes into effect. Most individuals are required to have health insurance. Penalties for those who fail to do so kick in, beginning at $95 a year per person, or up to 1 percent of a family's income, whichever is greater. (The penalty will increase in future years.) The penalty for an uninsured child is $47.50. Insurance companies cannot deny coverage on the basis of pre-existing conditions nor charge higher rates based on an applicant's sex or medical history. Policies must offer a basic package of benefits.

April 1, 2014: If you don't have insurance, you'll face a fine.

Jan. 1, 2015: Businesses with 50 or more workers must provide health benefits or pay fines.

4 How does it work? If you have a computer, go to Healthcare.gov or mnsure.org in Minnesota and create an account. Fill out an application and provide information such as household size, location and income. The exchange will determine whether you are eligible for Medicaid; if so, it will refer you there. (However, your application won't be able to be transferred to the proper state for processing until Nov. 1. But, your coverage will still start Jan. 1.)

If not, it will tell you how much of a subsidy you can receive. It will show you a list of health plans and their premiums and out-of-pocket costs, including deductibles and co-payments. If you decide to buy one of those plans, in most cases, you will be directed to the insurer's website to make the payment.

You can also fill out paper applications or apply over the phone at 1-800-318-2596 (federal), TTY: 1-855-889-4325 (federal), or 1-855-366-7873 (1-855-3MN-SURE).

No: People with employer-sponsored coverage generally won't buy on the exchanges, nor will those on Medicare, Tricare or other veterans health care plans. People who are in the country illegally will be barred.

Maybe: For businesses with 50 or fewer workers, the marketplaces will have a Small Business Health Options program, or SHOP, that will give employees more options than they now have. But it will be delayed until mid-month.