Yes. Even if you signed up mid-year, you must renew your coverage during the open enrollment period. For 2018 coverage, open enrollment is November 1, 2017 to December 15, 2017 in most states. All marketplace plans are offered on a calendar year basis. If you are receiving premium tax credits and want to ensure that you continue to receive the correct amount, you must return to the marketplace by December 15, 2017 to update your account information and select a plan. If you do nothing and are eligible, the marketplace will automatically renew you into the same plan with premium tax credits (if eligible) based on the latest household income data they have through their federal sources. However, for enrollees receiving premium tax credits and cost-sharing reductions who have not contacted the marketplace to update their information for the last two years and no IRS income information is available for the previous two tax years, the marketplace will discontinue premium tax credits and cost-sharing reductions unless the enrollee contacts the marketplace and receives an updated re-determination. (45 C.F.R. § 155.335; CMS, Guidance on Reenrollments and Redetermination for Exchange Coverage for 2018, July 13, 2017).