You will be charged a penalty if you did not have health insurance for more than three consecutive months in 2018, unless you qualify for an exemption. From 2019 onwards, you are still required by law to have Minimum Essential Coverage, and maintaining Minimum Essential Coverage is essential to qualifying for most special enrollment periods.
Beyond these legal requirements, insurance coverage is an important protection against unexpected, high medical costs. The cost of paying for medical care out of pocket is prohibitively expensive for most people, and while insurance coverage can also present a financial burden, it is far less than the cost of paying for an emergency situation or treatment for an unforeseen diagnosis without coverage.
To ensure that an insurance product provides comprehensive coverage and adequate financial protection, and to see if you qualify for premium tax credits, visit HealthCare.gov.