Open enrollment deadline for the Washington Health Benefit Exchange is today By Ryan Blethen, The Seattle Time Published: December 15, 2020, 8:22am Share: The homepage of Washington HealthPlanFinder. Tuesday is the last day to sign up for health insurance through the state for 2021. Open enrollment for the Washington Health Benefit Exchange closes tonight. Health insurance plans need to be purchased through the state’s marketplace by 11:59 p.m. for coverage beginning Jan. 1. As of Thursday, more than 200,000 people have selected a health insurance plan offered through the exchange, a 5% increase compared to the same period last year. Plans can be selected through the exchange website, WAhealthplanfinder.org, or by telephone at 1-855-923-4633.