Medicare enrollment window calculator: when can an employee sign up at 65?
Enter a date of birth and how the person is covered today to see the initial enrollment window and whether a group plan lets them wait. Built for HR teams that field Medicare questions from employees nearing 65.
Find the seven-month window around the 65th birthday.
Set the date of birth and the coverage situation. The dates update as you type.
COBRA and retiree coverage do not count as coverage through current work.
Your Medicare dates
A planning estimate, not legal advice. Confirm dates and penalties with Social Security or Medicare before an employee decides.
What is the initial enrollment period?
The initial enrollment period for Medicare lasts seven months. It begins three months before the month a person turns 65, includes the birthday month and runs three months after. Signing up in the three months before the birthday month lets coverage start on the first of the birthday month. Signing up in the birthday month or later starts coverage the month after.
How does a group health plan change it?
A person covered by a group plan through current work at an employer with 20 or more employees can usually delay Part B without a penalty. Smaller employers are different because Medicare often pays first for the employee. Our coordination of benefits page explains which plan pays first.
Common questions
Does the employee have to take Part A?
Part A is premium-free for most people with enough work history, so most people take it at 65. Someone with an HSA should talk to an advisor first, because Part A enrollment stops HSA contributions.
What about COBRA?
COBRA does not count as coverage through current work. A person on COBRA who delays Part B can face a penalty and a gap, and Medicare can end COBRA once it begins.
What is the Part B late penalty?
It is 10 percent of the Part B premium for each full 12-month period the person could have enrolled and did not. It lasts as long as the person has Part B.
What if the person keeps working past 65?
The person can keep the group plan and add Part B in a special enrollment period after the job or the coverage ends. An employee should confirm the rules with Medicare before delaying.
Laws and rules referenced
42 U.S.C. § 1395y(b)(1) and 42 C.F.R. § 411.172 — Medicare pays second to a group health plan for working aged employees of employers with 20 or more employees.
This tool gives estimates for education, not tax or legal advice. Rules change, so confirm your situation with a qualified advisor.
Talk to us about Medicare and your group plan
Book a 30-minute call and we will walk through how Medicare interacts with your plan for employees past 65. Visit us at 41000 Woodward Avenue, Suite 350 East, Bloomfield Hills, MI 48304, or call 248.370.8853.
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