Basically, the SEP EGHP (Employer/Union Group Health Plan) allows the Medicare beneficiary to enroll into a Medicare Part D plan or Medicare Advantage plan when you are still enrolled in your employer plan or the month the beneficiary is advised of the loss of creditable drug coverage and continues for two months from the loss of the coverage.
You will then be able to use the SEP to join a Part D drug plan when your drug plan ends or up to 2 months after the COBRA coverage ends.
So you will need to speak with your COBRA administrator or COBRA provider to confirm that your drug coverage is "creditable" and then coordinate the ending of your COBRA coverage with the start (effective date) of your Medicare Part D coverage.
To learn more about your Medicare Part D options and for assistance joining a Medicare Part D drug plan, please telephone a Medicare representative at 1-800-Medicare (1-800-633-4227). As reference, please see the Center for Medicare & Medicaid Services (CMS) Medicare & You Handbook:
"COBRA is a federal law that may allow you to temporarily keep employer or union health coverage after the employment ends or after you lose coverage as a dependent of the covered employee..... [i]f you take COBRA and [the COBRA coverage] includes creditable prescription drug coverage, you’ll have a Special Enrollment Period to get Medicare drug coverage (Part D) without paying a penalty when the COBRA coverage ends."As reference to this specific Special Enrollment Period, the Medicare Part D Manual notes:
"An SEP exists for individuals making an enrollment request into or out of an employer/union group-sponsored Part D plans, for individuals disenrolling from a Part D plan to take employer/union-sponsored coverage of any kind, and for individuals disenrolling from employer/union-sponsored coverage (including COBRA coverage) to enroll in a Part D plan. The SEP EGHP may be used when the EGHP allows the individual to make changes to their plan choices, such as during the employer’s or union’s “open season,” or at other times the employer or union allows.Bottom Line: You can confirm with your former-employer or COBRA administrator that your EGHP or COBRA drug coverage is creditable and that the effective (starting date) date of the Medicare Part D plan will correspond with the end of your COBRA benefits.
This SEP is available to individuals who have (or are enrolling in) an employer or union plan and ends 2 months after the month the employer or union coverage of any type ends.
The individual may choose the effective date of enrollment or disenrollment, up to 3 months after the month in which the individual completes an enrollment or disenrollment request. However, the effective date may not be earlier than the first of the month following the month in which the request was made. The effective date also may not be earlier than the first day of the individual’s entitlement to Medicare."
Sources include:
2022 Medicare & You Handbook
Medicare Prescription Drug Benefit Manual, Chapter 3 - Eligibility, Enrollment and Disenrollment, Updated: August 19, 2011 (Revised: November 16, 2011, August 7, 2012, August 30, 2013, August 30, 2014, July 6, 2015, September 1, 2015, September 14, 2015, December 30, 2015,May 27, 2016, August 25, 2016, June 15, 2017, July 31, 2018 & August 12, 2020)
https://www.medicare.gov/supplements-other-insurance/how-medicare-works-with-other-insurance/cobra-7-important-facts
COBRA Continuation Coverage Questions and Answers
https://www.cms.gov/CCIIO/Programs-and-Initiatives/Other-Insurance-Protections/cobra_qna
COBRA Continuation Coverage Questions and Answers
https://www.cms.gov/CCIIO/Programs-and-Initiatives/Other-Insurance-Protections/cobra_qna