Hsa eligibilty / medicare issue

[RWG1950]

Customer is age 67 still works full-time & has a HDHP at work and HSA contributions have been shown on his previous W-2's.
He's not yet on social security. Wife is age 67 and has been on social security and Medicare part "A" & "B" since mid-2017.
Wife called me today & said her husband visited the local SS office last month & they told him he qualified to receive 1/2 of her benefit until he goes on his own.
She said they (SS) will backdate this payment eligibility to May of 2018 & he'll get a lump sum for these past payments in the near future.
Because he's still working & on his employer's HDHP, he hasn't signed up for Medicare part "B" yet but they did apparently enroll him in part "A" last month (presumably also backdating this to May 2018)
I know the rules state you can't contribute to an HSA when you are enrolled in Medicare, but does this part "A" enrollment backdating mean he became ineligible to make HSA contributions as of May/2018 ?
If so, how should this be handled on the 2018 return ?
Have not seen his 2018 W-2 yet but my guess is it'll show about $4,000 in HSA contributions.
Thanks for any comments.

[Gretel]

See below for what I kept on file for a client in a similar situation (I believe this is exactly the same in the Medicare handbook, and yes, it's ugly:

It's a pdf so I don't know how to direct link, but if you google "deciding whether to enroll in medicare part a and part b when you turn 65", the first result should be a pdf from CMS. Your situation is specifically addressed on page 4:

I have a High-Deductible Health Plan AND a Health Savings Account (HSA)
Once you enroll in any part of Medicare, you won’t be able to contribute to your HSA. If you would like to continue making contributions to your HSA, you can delay both Part A and Part B until you (or your spouse) stop working or lose that employer coverage. You will NOT pay a penalty for delaying Medicare, as long as you enroll within 8 months of losing your coverage or stopping work (whichever happens first).
You should talk with your employer benefits manager about whether it makes sense to delay Part A and Part B.
NOTE: If you qualify for premium-free Part A, your coverage will go back (retroactively) up to 6 months from when you sign up. So, you should stop making contributions to your HSA 6 months before you enroll in Part A and Part B (or apply for Social Security benefits, if you want to collect retirement benefits before you stop working).

[RWG1950]

HSA / MEDICARE :
This customer has now (in Feb 2019) taken steps to remove the HSA contributions he was ineligible to make in 2018 and also those made in 2019.
Because of the timing, both of these distributions will probably be reported on his 2019 1099-SA form.
The withdrawal of his 2019 contribution won't be an issue until the 2019 return is filed.
But the amount withdrawn that resulted from his 2018 ineligible contributions won't show up on his 2018 form 1099-SA - it'll be on the 2019.
Should this 2018 withdrawal amount be shown as income on his 2018 or 2019 form 8889 ?
Thanks for comments

[Gretel]

Attached document that I pieced together might be helpful to you. However, I did not have to deal with a prior year. I tried to attach but I got the message that I am not authorized to attach anything. If you give me your e-mail I can e-mail it to you.