Open enrollment is the one time each year you get to choose your health insurance — and for most people, it's also the one time each year they quietly lose thousands of dollars without realizing it. Every fall, millions of Americans auto-renew their health plan, glance at the premium, and move on. Then January arrives with a surprise: their doctor is out of network, their prescriptions cost triple, or their deductible jumped and nobody told them. Don't let that be you. Here are the 5 mistakes that cost people thousands during open enrollment — and exactly how to avoid each one. Know Your Dates First Before anything else, know which window applies to you: ACA Marketplace (federal): November 1, 2026 – January 15, 2027 State exchanges: Same general window (check your state's site for exact dates) Medicare open enrollment: October 15 – December 7, 2026 Employer plans: Usually October–November (check with your HR department) The single most important date: enroll by...