She Divorced at 68 and Took COBRA. Medicare’s Eight-Month Part B Clock Kept Running.

A 68-year-old finalizes her divorce and loses coverage under her husband’s active large-employer health plan. She elects COBRA so she can keep the same doctors and insurance card while everything else in her life is changing. It feels like breathing room. After all, COBRA after divorce can last as long as 36 months. Medicare gives her eight.

Because she delayed Medicare Part B while covered through her spouse’s current employment, losing that coverage starts a Special Enrollment Period (SEP). COBRA can keep the employer plan going, but it does not stop Medicare’s enrollment clock.

Tick-Tock

Medicare gives someone who delayed Part B because of current-employment coverage eight months to enroll after the employment or that coverage ends, whichever comes first. For this woman, the important date is when the divorce ends her coverage as the employee’s spouse. The COBRA policy that replaces it is continuation coverage, not coverage based on current employment. That distinction can be expensive.

If she assumes she can wait until COBRA expires, she could sail right past Medicare’s eight-month window while still carrying an insurance card that looks perfectly valid. Worse, COBRA itself may not fill the hole she expects it to fill. Medicare warns that when someone is eligible for Medicare but not enrolled, COBRA may pay only a small portion of the bill. The future late-enrollment penalty is not necessarily the first financial problem.

The Penalty Can Follow Her for Life

Miss the SEP and she generally has to enroll during Medicare’s General Enrollment Period, which runs from January 1 through March 31. Part B then starts the month after enrollment. The late-enrollment penalty adds 10% to the Part B premium for each full 12-month period she could have had Part B but did not.

At the 2026 standard premium of $202.90, one full year produces an extra roughly $20.30 a month. The percentage generally remains attached for as long as she has Part B, and the dollar penalty rises when the standard premium rises. Waiting through a long COBRA period can therefore turn temporary continuation coverage into a permanent Medicare surcharge. (We cataloged this and other Medicare premium traps in a free Medicare guide: Medicare’s Hidden Bills.)

One Door Is Still Open

There is an important piece of good news in the timing. Because she has never enrolled in Part B, her one-time federal Medigap open enrollment period has not started yet. It begins when she finally gets Part B and lasts six months. During that window, a Medigap insurer cannot reject her or charge more because of her health. So missing the Part B SEP can create a penalty and coverage problems, but it does not automatically cost her the protected Medigap window too. That clock follows Part B.

Part D Uses Yet Another Clock

Prescription coverage adds one more layer. COBRA does not count as current-employment coverage for the Part B SEP, but its prescription benefit may still qualify as creditable drug coverage for Part D. If it does, she can generally keep that drug coverage without starting the Part D late-enrollment penalty clock.

If it does not, going 63 consecutive days without Part D or other creditable prescription coverage can trigger a separate lifetime penalty. Same COBRA policy. Two Medicare programs can treat it differently.

Act Before COBRA Becomes the Default

Before assuming the continuation policy buys plenty of time, these three checks can protect the Medicare coverage that comes next:

1. Mark the date the active employer coverage ended and count the eight-month Part B SEP from there. Do not use the COBRA expiration date.
2. Apply for Part B while that window is still open. CMS-40B handles the enrollment, while CMS-L564 documents the former employment-based coverage.
3. Ask the COBRA administrator in writing whether the prescription coverage is creditable for Medicare Part D and keep that notice with the enrollment records.

COBRA can keep the same insurance card in her wallet after the divorce. What it cannot do is keep Medicare’s clock from moving.

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