https://www.irs.gov/affordable-care-act/individuals-and-families/questions-and-answers-on-the-indivi...

1. Religious conscience. You are a member of a religious sect that is recognized as conscientiously opposed to accepting any insurance benefits. The Social Security Administration administers the process for recognizing these sects according to the criteria in the law.
2. Health care sharing ministry. You are a member of a health care sharing ministry.
3. Indian tribes. You are (1) a member of a federally recognized Indian tribe or (2) an individual eligible for services through an Indian care provider.
4. Income below the income tax return filing requirement. Your income is below the minimum threshold for filing a tax return. The requirement to file a federal tax return depends on your filing status, age and types and amounts of income. To find out if you are required to file a federal tax return, use the IRS Interactive Tax Assistant (ITA).
5. Short coverage gap. You went without coverage for less than three consecutive months during the year. For more information, see question 22.
6. Hardship. You have suffered a hardship that makes you unable to obtain coverage, as defined in final regulations issued by the Department of Health and Human Services. See question 21 for more information on claiming hardship exemptions..
7. Affordability. You can’t afford coverage because the minimum amount you must pay for the premiums is more than a certain percentage of your household income.
8. Incarceration. You are in a jail, prison, or similar penal institution or correctional facility after the disposition of charges against you.
9. Not lawfully present. You are not lawfully present in the U.S. and are not a  U.S. citizen, or U.S. national.

Review the instructions for Form 8965, Health Coverage Exemptions, for more information.