I have a technical Medicare eligibility question.

I have health insurance through my employer. I turned 65 in July, 2018; DH turned 65 in October 2018. We both applied for Medicare A and are enrolled.

In late September, I decided to retire as of Dec 1, 2018. My employment and my employee health benefits, under which my DH is covered, will end on Nov 30.

I have applied for my retiree benefits to start Dec 1.

I've been through the mill with the SS office. I was initially told that there was no problem with DH and I applying for Part B as part of the Special Enrollment Period that exists for us as we have had credible coverage. So no problem, right?

Except, first they lost the Part B paperwork.

When I went back today, they told me that, even though my husband has been covered under my employee benefits for 16 years, because he did not apply for Medicare Part B during his birthday month (October) he is NOT eligible for Part B to start until Jan 1.

I told them I thought that that wasn't possible; CMS couldn't possibly say that his IEP trumped the SEP.

They insisted (went through 3 agents, including the "expert") who told me that that is the correct interpretation.

Because I had proof that the paperwork from my employer was signed during the month of October (his birthday month) they say that he's eligible for coverage that starts Nov 1 (even though I'm still employed). He can be eligible for Nov 1 OR Jan 1. Just NOT Dec 1.

Does anyone have anything they can point to that says that this is not the correct interpretation of the law?